Tool to compare large numbers of PDF files? [closed]

Because there is no such tool available that we have written one. You can download the i-net PDF content comparer and use it. I hope that help other with the same problem. If you have problems with it or you have feedback for us then you can contact our support.

There is actually a diffpdf tool.

http://www.qtrac.eu/diffpdf.html

Its weakness is that it doesn't react well when additions make new text shift partially to a new page. For instance, if old page 4 should be compared to the end of page 5 and the beginning of page 6, you'll need to shift parameters to compare the two slices separately.

I've used a home-baked script which

• converts all pages on two PDFs to bitmaps
• colors pages of PDF 1 to red-on-white
• changes white to transparent on pages of PDF 2
• overlays each page from PDF 2 on top of the corresponding page from PDF 1
• runs conversion/coloring and overlaying in parallel on multiple cores

Software used:

• GhostScript for PDF-to-bitmap conversion
• ImageMagick for coloring, transparency and overlay
• inotify for synchronizing parallel processes
• any PNG-capable image viewer for reviewing the result

Pros:

• simple implementation
• all tools used are open source
• great for finding small differences in layout

Cons:

• the conversion is slow
• major differences between PDFs (e.g. pagination) result in a mess
• bitmaps are not zoomable
• only works well for black-and-white text and diagrams
• no easy-to-use GUI

I've been looking for a tool which would do the same on PDF/PostScript level.

Here's how our script invokes the utilities (note that ImageMagick uses GhostScript behind the scenes to do the PDF->PNG conversion):

$ convert -density 150x150 -fill red -opaque black +antialias 1.pdf back%02d.png
$ convert -density 150x150 -transparent white +antialias 2.pdf front%02d.png
$ composite front01.png back01.png result01.png # do this for all pairs of images

I don't seem to be able to see this here, so here it is: via superuser: How to compare the differences between two PDF files? (answer #229891, by @slestak), there is

https://github.com/vslavik/diff-pdf

(build steps for Ubuntu Natty can be found in get-diff-pdf.sh)

As far as I can see, it basically overlays the text/graphics of each page in the pdf(s), allowing you to easily see if there were any changes...

Cheers!

We've also used pdftotext (see Sklivvz's answer) to generate ASCII versions of PDFs and wdiff to compare them.

Use pdftotext's -layout switch to enhance readability and get some idea of changes in the layout.

To get nice colored output from wdiff, use this wrapper script:

#!/bin/sh
RED=$'\e'"[1;31m"
GREEN=$'\e'"[1;32m"
RESET=$'\e'"[0m"
wdiff -w$RED -x$RESET -y$GREEN -z$RESET -n $1 $2