PDF md5 checksums changing

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PDF md5 checksums changing

Postby AndrewCampbell on Tue Dec 05, 2017 3:24 am

If I generate a PDF from Flare, and then immediately generate a second copy of the PDF using identical settings, I get two PDFs that have identical content - which is what should be happening.

However, the md5 checksums of the two versions of the file are different, presumably because metainformation of some kind is embedded in the PDF. Is there any way of stopping Flare adding this metainformation?

I'd like to be able to generate md5 checksums to quickly check if two PDFs are different - that way I can avoid using the painful Acrobat PDF Compare function. I would welcome suggestions for other PDF comparison techniques, particularly command-line based options.
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Re: PDF md5 checksums changing

Postby trent the thief on Tue Dec 05, 2017 1:22 pm

Hi Andrew,

If you check the properties in the PDF's (CTRL+D) you'll find that the File Created and File Modified dates are different. That's enough to throw off the MD5 calculation. There might be a PDF extension that only compares content, but it probably won't be free. The same applies to third-party tools
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Re: PDF md5 checksums changing

Postby AndrewCampbell on Fri Dec 08, 2017 2:04 am

Ah! Thanks, I never thought of that.

I'll play around with a script that will change those dates and see what I can come up with (I tend to live on the command line, so I am naturally attracted to problems that can be fixed with a script).
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