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disable Adobe PDF doc for edit, print & SAVE?
March 15, 2006 4:53 PM   Subscribe

How to fully protect an Adobe pdf? I want to post an exam temporarily on the net for my class, and I'm using Adobe Pro 7.0's security functions to disable editing and printing functions (so students can't easily print and circulate the exam). The doc can still be saved, however. Adobe forums seem to have no idea how to disable the SAVE pdf function....

Alternately, I've toyed with posting images and disabling the 'save as' and IE pic toolbar with html/java - but that doesn't preclude printing either.

css? (I only need to impede the casual user--I realize printscreen copies are unavoidable). i need to do this NOW...any help appreciated.
posted by rexruff to Computers & Internet (31 answers total)
 
If they can't print from Adobe they'll just hit the print screen button, save it as an image and print that way. Not the least bit hard. If they can see it on their computer, they can print it out.
posted by hindmost at 5:06 PM on March 15, 2006


I'm sorry to say: you cannot protect it from your students, if your goal is to prevent easy printing and circulation of the document.

Here's why: all computers can take screenshots, and kids are blazingly fast with their computers these days. Any slight inconvenience you might introduce with your attempts to lock it will be more than outweighed by the social status a kid will gain by distributing copies to those who want them.

So as much as bim's comment above was a bit grumpy, it was correct: your only protection is to either vary the test significantly each time, or to only hand out copies during class (and collect them at the end of class) -- and even that second method won't stop a kid from copying if they're determined (pocket scanners, cell phone cameras, small tape recorder to murmur the questions into).
posted by davejay at 5:07 PM on March 15, 2006


Unfortunately, rex, if they can _see_ it the game is already over. All they have to do is "printscreen" and wham -- one printed copy.

Sure, they'll have to do that a couple of times, and it'll slow them for all of a minute. Alternatively, it's amazing what you can do with a pen and a piece of paper these days....

On preview: damnit.
posted by coriolisdave at 5:07 PM on March 15, 2006


I'm not familiar with Adobe DRM, but I'd guess that preventing saving isn't possible since to view the PDF the user has to have already downloaded it, so it'll be cached somewhere.
posted by matthewr at 5:08 PM on March 15, 2006


Actually, all they have to do is use a PDF viewer other than Adobe's, and they can print and edit it, too.

What you're hoping to accomplish cannot be done in the manner you wish to accomplish it.
posted by majick at 5:10 PM on March 15, 2006


Wow. Those are amazingly fast, judgemental, and not at all helpful. Read this again:
(I only need to impede the casual user--I realize printscreen copies are unavoidable).

I realize I'm asking a highly tech literate population (maybe that was my mistake?), but you'll have to trust me that I know my students, know what their computer literacy skills are like, and that I 'put in an effort.'

Sheesh yourselves.
posted by rexruff at 5:13 PM on March 15, 2006


There's no way to restrict saving in the most recent version of Adobe, so I very much doubt there is any way to do so in your earlier version.

The security in Acrobat is pretty much aimed at being able to distribute a document without fear of changes or someone lifting text, so I don't think it was designed with a frame of mind where it would occur to inhibit saving.

As was said above, what you wish to do cannot be done in the way you wish to do it.
posted by tiamat at 5:19 PM on March 15, 2006


rexruff:

The best I can think about is watermarking the PDF's. Somthing in the line of "I know you can copy it, but I'll know it was you). Yeah, beatable, but yet creepy enough to give kids second thoughts.

Of course, not an easy job to implement.
posted by qvantamon at 5:25 PM on March 15, 2006


Well, majick's point still stands. Acrobat is the standard pdf viewer, but by no means the only one, and any proprietary drm in Acrobat is going to be ignored by the other programs.

If you want to foil a casual copier, put each question on a separate page, so that they'll have to print-screen and then print out 20 pages of mostly blank paper. Also include a lot of dark areas and color so that they'll have to print that out too, mohaha.

But the larger point, that you can't have complete security, bears being mentioned, because it leads to a corrollary: that any method of protecting a document that tries to get around this basic insecurity will inevitably be annoying to the user (see the above).
posted by Hildago at 5:27 PM on March 15, 2006


Ah, what you want to do is doable, but very expensive. Check this out.

The answer (at the bottom of the page) refers to Adobe Policy Server and provides links to a couple of competitors. Adobe doesn't publish pricing and the competitors cost thousands of dollars.

The thing is, there's no point disabling 'save' in Acrobat itself because you could just right click the document and save as. So you're back to using javascript anyway.

To be effective, you need 'phone home' type DRM. And that's going to cost a small fortune and require a dedicated server. Do you really distrust your students that much?
posted by jedicus at 5:29 PM on March 15, 2006


How about embedding the PDF in a page, with a giant clear gif over the top of it? Most users would right click to save and be presented with the option to save the clear gif.
posted by mathowie at 5:30 PM on March 15, 2006


Sorry for the grumpiness. I'll kick the diplomacy up a notch. :)
posted by bim at 5:34 PM on March 15, 2006


Disabling "save as" in the pdf won't do much -- they can just save the whole pdf from your website, given the url.

Displaying a jpeg or gif and disabling "save as" in javascript is likely going to be ineffective if they use Firefox, and can pretty well be defeated by any browser that allows a "display source".

And as you acknowledge, printscreen always works.

Basically, you can't do this unless you use some proprietary viewer, and even that's difficult -- the viewer would have to somehow inhibit/replace the printscreen functionality of the OS.

Sorry you're finding the responses judemental (they don't read that way to me), but you're getting free, accurate, and honest advice. You're not getting teh answer you want, but that's only because that's not the real answer.
posted by orthogonality at 5:34 PM on March 15, 2006


How about embedding the PDF in a page, with a giant clear gif over the top of it? Most users would right click to save and be presented with the option to save the clear gif.

if they know enough to right click, wouldn't they just go up to the file menu and go save-page-as->webpage, complete?
posted by juv3nal at 5:35 PM on March 15, 2006


How about embedding the PDF in a page, with a giant clear gif over the top of it?

Hey, that's clever.
posted by qwip at 5:39 PM on March 15, 2006


I have to ask -- why can't they just have a copy of the exam???
posted by bim at 5:43 PM on March 15, 2006


As others have said, this can be defeated with just a modicum of tech-savviness, and once it's defeated, it'll spread. Another way to defeat it, if you're planning on putting it up on the web: any one of the "view PDF as HTML" online filters out there (an example).

I re-read all the answers to date and I don't see any that are judgemental. They are, however, mostly all correct.
posted by aberrant at 5:44 PM on March 15, 2006


I'm not CSS-saavy but couldn't you use differing screen and print stylesheets? Set it up in a div so that the when the student goes to print, the print stylesheet sets the font to white. Combine that with Matt's clear .gif suggestion and you've defeated saving and printing for the casual user.
posted by junesix at 5:47 PM on March 15, 2006


What I'm about to say shouldn't be read in any way as "grumpy." With that said:

It ain't gonna happen. Stop wasting time trying to do it. You can't. The answer to your question is, "You can't. Period." Too many easy solutions for even the least computer literate.
posted by pwb503 at 5:52 PM on March 15, 2006


I know we've beaten this dead horse here but I just want to point out that you don't even have to go to the depths of print screen. There are utilities out there (example) that you can download and run that will instantly remove all protection from the PDF file -- copy/paste, modify, print, everything. It boggles my mind why people bother to distribute PDFs that you can't copy and paste from, since it takes literally seconds to run it through one of those programs. These features should never be used when actual security is needed, just as a minor inconvenience.

The suggestion to convert the exam to JPG or GIF and display it as the background image of the page with a clear GIF on top of it is a good one. The imdb uses this trick for movie posters so that you can't just right click and "copy image location" or "save image as", since you'll get the transparent GIF instead of the poster.
posted by Rhomboid at 5:57 PM on March 15, 2006


casual user doesn't matter whatsoever, because once the nerdiest student figures out how to get a paper copy, making 200 copies is very easy and they'll likely just pass the stack around in front of you next class period while you blather on.
posted by kcm at 6:26 PM on March 15, 2006


How do you scroll a PDF if there's a clear gif over it?
posted by sbutler at 6:34 PM on March 15, 2006


Convert the pdf to a jpeg, put a class attribute in the img tag with the value 'test'. Then, add this to the head tag:
<style type="text/css" media="print">
.test{display:none;}
</style>
It'll stop most casual users from managing to print this. It's also more or less how Google Print does this, FWIW.
posted by matthewr at 6:39 PM on March 15, 2006 [1 favorite]


Hey all,

Wow, this got good. Thanks for the feedback, and the creative ideas. Tiamat & Matthewr answered my question most directly, but the embedding, css, watermarking, and multiple-page ideas were the kinds of stuff I was actually looking for…. that said, I do appreciate all the specifics about all the ways to foil the pdfs…..amazing how fast this stuff changes.

To satisfy curiosity, let me just say that I’m putting the exam online for 48 hours to give them an opportunity to go back over their response sheets privately with the full text, beyond the review we did in class. I fully agree that multiple choice tests suck generally, but I’m finding them an unfortunate necessity with huge state university classes, especially a general ed required course. And you’d be surprised how much work it is developing and testing a reliable multiple choice exam-- while the exam does change slightly every semester, it just seems wise to make some effort to prevent _casual_ recirculation of specific questions. It’s not that I don’t trust my students—I just don’t see a reason to tempt them either.

As for tech literacy, I’m doing my best to drag them online, so if they figured out how to beat adobe, I’d almost be happy. These are hardworking students juggling a full schedule and 20-40 hrs/wk outside jobs, and getting them to check a class website regularly has been tough.

Thanks all. Really.

p.s. Oh yeah, and pwb503, you really need to get out from behind that computer once in a while.
posted by rexruff at 6:52 PM on March 15, 2006


For the record, rexruff, I see where you're coming from with the multiple choice tests.

As lousy as they are, I've had to use them too at times -- having taught full time at 3 different colleges/universities for about 10 years overall.

But it is a great help to students to have something to practice on. They really do appreciate. And as much as a pain in the butt it was, I always made up a new test. Every time. Multiple choice or otherwise. It's part of the job, IMHO.

No hard feelings, but that's where I was coming from.
posted by bim at 7:18 PM on March 15, 2006


Even as a jpeg, with all that great css stuff, here is what I would do to save and circulate your exam (not trying to be grympy, just saying):

View source.
open notepad
put into notepad: "blah"
save as: blah.html
open blah.html in IE
right click, save as.

I'm not sure if .htaccess rules will prevent this possibility, but it's one more security issue to worry about (and not really that sophisticated, if you ask me).
posted by antifuse at 2:33 AM on March 16, 2006


oh, and I'm a dumbass... that "blah" link should be

"<a href="[location of jpeg file]">blah</a>"
posted by antifuse at 2:48 AM on March 16, 2006


To summarise, what you're trying to do is impossible.

If I can view a PDF in any way, I can convert it to a completely unrestricted format that I can change, print or re-distribute with no protection.

And if these are students, they're probably sufficiently skilled and incentivised to do it.
posted by quiet at 3:11 AM on March 16, 2006


Wait, these are university students? If they can't figure out how to get past these restrictions, fail 'em. It's practically a lifeskill.
posted by bonaldi at 4:10 AM on March 16, 2006


I have tried none of these, but here are some things to try in combination:

Write a basic java applet using Quicktime for Java to play a SMIL file which encapsulates a slide show of the exam that is accessible to the server but not available over the network.
Use some referer checking on requests for the applet to verify the request came from the parent HTML page.
Link to applet targets new window with all chrome turned off.
Use CSS to display:none all object/embed elements in print media.
Use Javacript to intercept all key strokes, eating these events—not even sure if this will work for every keystroke.
Purchase and horde the world's supply of writing implements and surfaces.

Seriously though, anything you put on a network can be captured for redissemination. Further, the effort going into the act of capturing will be less than the effort you put into protection—generally by several orders of magnitude. It's certainly less work to write a new test every time the course is offerred. If the exams are multiple choice, you can even write an app that creates the exam from a pool of questions you add to each semester, randomly sequencing the answers for each question and probably for less work than what I described above.
posted by Fezboy! at 10:38 AM on March 16, 2006


Seriously...no offence intended, but as far as I can see very few of you think outside the box. Look at every problem as a personal challenge and you will figure out a solution every time. It's your destiny!

Why not have a copy of the pdf, slightly different of course, so slightly that they might not notice the difference, for every single student at their own url that you give only them access to. Use usernames and passwords that you create and they can't change. Have your database track what ip the login comes from as a backup security measure.

At least you will know who looked at the docs, and since not all of them do apparently, you can also see patterns of logins with the same username and password from different ip's. Since they won't know about the ip tracing, you will know how you did it but they won't.

If it was good enough for catching spies it will no doubt work fairly well here. It doesn't matter that you can't stop them. You can embarrass them in class. It will soon stop.

I'm sure these kids are bright as hell, but if you want to stop/slow down/stop casual users from doing this....think outside the problem and look at it a different way.
posted by bosnm at 5:37 PM on October 23, 2006


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