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PDFDiff for Mac

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Posted by MadaboutDana
Jun 7, 2021 at 10:13 AM


Yo folks, just a quickie that’s tangentially relevant to outliners, but especially to citation apps or equivalent.

I’m just testing out a new app for macOS called PDFDiff (available from the Mac App Store). It allows you to compare a couple of PDFs, using colours to highlight the differences between the two PDFs.

I was initially full of scepticism, because I’ve used many PDF differential comparison apps over the years and they’ve all been (severely) flawed, especially when comparing two longer PDFs. But so far, PDFDiff is proving exceptionally capable. I’m using it to compare two annual reports (2019 and 2020), one 140 pages, one 110 pages long, and despite the differences in length and the major structural differences in various areas, the app is making an unbelievably competent stab at highlighting the changes.

The only thing it hasn’t spotted so far is the transfer of an auditor’s report from one part of the document to a completely different part of the document – the report is pretty much identical from one year to the next, but clearly the 60-page shunt caused PDFDiff to miss it. Having said that, it’s successfully “found” plenty of other major shifts/text transfers.

As anyone involved in translation knows, dealing efficiently with PDFs is quite difficult, because depending on the competence of the layout artist, the text is more or less tricky to extract into something more writer-friendly (which one can then feed into a CAT tool for close comparison). This new app (with a footprint of just 4MB – yes, really!) is a valuable addition to the translator’s toolset.

So: apologies for the not-entirely-outliner-related post, but it’s definitely a goodie for information/knowledge management!



Posted by Amontillado
Jun 7, 2021 at 12:53 PM


I am not well informed about PDF internals, but I know enough to see comparing them has got to be challenging. Neat application!


Posted by Darren McDonald
Jun 8, 2021 at 02:30 PM


@Bill, Is this the app that was developed by Alexander Jaehrling? I just wanted to confirm as a search on the Apple app store comes up with several similar apps with similar names.


Posted by MadaboutDana
Jun 9, 2021 at 08:11 AM


Yes, that’s right, Mr Jaehrling is the developer.

Ah, I see what you mean, there are a few apps with PDF Diff somewhere in the name. One of the more irritating aspects of the App Store, I find.



Posted by Darren McDonald
Jun 10, 2021 at 12:10 PM


Thanks @Bill. I was pretty sure from your good description that it was the app by Alexander Jaehrling. Thanks again! :)


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