Looking for program to compare PDF files.

May 19, 2023 12:37 PM

When it comes to comparing two PDF files, is there ANYTHING better than the internal Adobe Acrobat Pro "Compare files" feature?

At work we are now being required to document changes in a document from one version to the next, and it must be automatic. (For years we did it manually, which was good enough, but the higher ups think that computers can fix everything, or something.)

The compare feature in Adobe Acrobat Pro is useless. An average compare yields 600 results, when in reality it's about 20 to 50. (If "ignore footers" wasn't turned off, it would be much worse.) It gets confused when text reflows to a new page in the new version, resulting in 10 new "differences." If "compare graphics" is turned on, it thinks that every page is a graphic and gets even more confused. If turned off, the graphics are ignored, even when they have text in them that is different. It can't deal with degree symbols. If one word in a sentence is changed, it sometimes (not always) highlights the whole sentence. You get the idea.

Anyhoo, is there anything better out there? I downloaded half a dozen trial versions of different programs, but they all seem to use the Adobe engine and yield similar results. We really like the output in Adobe (a new file that highlights the differences and allows you to compare line-by-line), we just hate the fact that it's so lousy.

I'm tired of downloading trials, so please only respond if you have used a program that works (free or not free is fine). Also, we have to use PDFs and can't just use tracking in Word or our other programs. Thank you!

posted by Melismata to Computers & Internet (5 answers total)

At work, one of the tools we use (by which I mean I frequently run and I monitor the results of) is Applitools, which looks for differences between a "baseline" image and a "test" image. In this case, it's old and new images of web pages, and any pixels that look different between two screenshots of the same page will get highlighted as differences to validate. Sometimes the differences are what we want to see, and sometimes they mean something broke.

I've been curious about its ability to do the same thing with PDFs, but I haven't actually tested the ability because the feature isn't part of what my employer pays for. But Applitools says it's possible.
posted by emelenjr at 1:20 PM on May 19, 2023

I have used ABBYY FineReader for this in my former job. It wasn't perfect, but it worked well enough for me, and seemed to be... smarter? than Adobe's "Compare" tool. In the blurb on their site about comparing documents, it says:

FineReader will only display the differences that affect the meaning of the document and disregard insignificant differences such as formatting or line breaks. This lets you review documents 5 to 20 times faster* so you can focus on what is most important, simplify your work, and reduce the chances of missing something that matters. You can even manually disregard differences that are not relevant for your task, and they will no longer appear in the list of comparison results.

posted by xedrik at 1:47 PM on May 19, 2023 [1 favorite]

PDF24 is completely free and has it as an option. I haven't used that particular tool, but the others I have worked well.
posted by kathrynm at 2:00 PM on May 19, 2023 [2 favorites]

How is the department creating the document? If you can track changes/redline in the source, it will be much more meaningful in a document than once it has lost all context by being converted to PDF.

PDF is often little more than marks on a page. Your (MS Word?) source document has the full edit history. It might even capture some of the human intention behind the changes. Acrobat's diff facility is about as good as it can be, working at the marks-on-a-page level.

Very large law firms can afford amazing document management suites that turn scanned paper and random PDFs into coherent documents with revision histories. I suspect at the lowest level it may involve very underpaid people in a faraway country re-keying stuff.
posted by scruss at 8:56 AM on May 20, 2023 [1 favorite]

Many PDF tools compare by overlaying the “page”, which is great for some uses (e.g. when I need to compare architectural plans), but less helpful when text changes cause text to reflow.

I have not tried it, but this looks promising, as it focuses on the CONTENT, not on the APPEARANCE on the page.

https://app.copyleaks.com/text-compare/compare-pdf-files
posted by misterbrandt at 11:23 AM on May 21, 2023