Tool to compare large numbers of PDF files?

Testing Problem Overview

I need to compare large count of PDF files for it optical content. Because the PDF files was created on different platforms and with different versions of the software there are structural differences. For example:

the chunking of text can be different
the write order can be different
the position can be differ some pixels

It should compare the content like a human people and not the internal structure. I want test for regressions between different versions of the PDF generator that we used.

Testing Solutions

Solution 1 - Testing

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.

enter image description here

Solution 2 - Testing

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.

Solution 3 - Testing

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

Solution 4 - Testing

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!

Solution 5 - Testing

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

Solution 6 - Testing

I think your best approach would be to convert the PDF to images at a decent resolution and than do an image compare.

To generate images from PDF you can use Adobe PDF Library or the solution suggested at https://stackoverflow.com/questions/75500/best-way-to-convert-pdf-files-to-tiff-files.

To compare the generated TIFF files I found GNU tiffcmp (for windows part of GnuWin32 tiff) and tiffinfo did a good job. Use tiffcmp -l and count the number of lines of output to find any differences. If you are happy to have a small amount of content change (e.g. anti-aliasing differences) then use tiffinfo to count the total number of pixels and you can then generate a percentage difference value.

By the way for anyone doing simple PDF comparison where the structure hasn't changed it is possible to use command line diff and ignore certain patterns, e.g. with GNU diff 2.7:

diff --brief -I xap: -I xapMM: -I /CreationDate -I /BaseFont -I /ID --binary --text

This still has the problem that it doesn't always catch changes in generated font names.

Solution 7 - Testing

Our product, PDF Comparator - http://www.premediasystems.com/pdfc.html" - will do this quite elegantly and efficiently. It's also not free, and is a Mac OS X only application.

Solution 8 - Testing

Based on your needs, a convert to text solution would be the easiest and most direct. I did think the bitmap idea was pretty cool.

Solution 9 - Testing

blubeam pdf software will do this for you

Solution 10 - Testing

You can batch compare pdf files with Tarkware Pdf Comparer. But it's not free and requires Adobe Acrobat.

Content Type	Original Author	Original Content on Stackoverflow
Question	Horcrux7	View Question on Stackoverflow
Solution 1 - Testing	Horcrux7	View Answer on Stackoverflow
Solution 2 - Testing	jabial	View Answer on Stackoverflow
Solution 3 - Testing	akaihola	View Answer on Stackoverflow
Solution 4 - Testing	sdaau	View Answer on Stackoverflow
Solution 5 - Testing	akaihola	View Answer on Stackoverflow
Solution 6 - Testing	danio	View Answer on Stackoverflow
Solution 7 - Testing	Peter Truskier	View Answer on Stackoverflow
Solution 8 - Testing	user602475	View Answer on Stackoverflow
Solution 9 - Testing	M Jenkins	View Answer on Stackoverflow
Solution 10 - Testing	erks	View Answer on Stackoverflow