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I'm looking for a good program to show me the differences between two similar pdf files. In particular, I'm looking for something that doesn't just run diff on an ascii version (with "pdftotext") of the files. This is what pdfdiff.py does.

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Does it have to be open source and free? – Rinzwind May 6 '11 at 19:56
    
@Rinzwind: That would be preferable, of course. – krumpelstiltskin May 6 '11 at 20:09
    
inetsoftware.de/other-products/pdf-content-comparer/… 2.2 here states it can be used under Linux (runPDFC.sh) but the file is not in the archive (only a bat...) but it is java so maybe renaming it(?) – Rinzwind May 6 '11 at 20:24
    
@Rinzwind: i don't know enough about java to figure out why it isn't running. i do: java -cp . -jar PDFC.jar but get a java.lang.NoClassDefFoundError :( – krumpelstiltskin May 6 '11 at 21:47
    
@Rinzwind: i ran this on windows; the program is terrible. it creates png that are illegible. – krumpelstiltskin May 6 '11 at 22:55

You can use DiffPDF for this. From the description:

DiffPDF is used to compare two PDF files. By default the comparison is of the text on each pair of pages, but comparing the appearance of pages is also supported (for example, if a diagram is changed or a paragraph reformatted). It is also possible to c> ompare particular pages or page ranges. For example, if there are two versions of a PDF file, one with pages 1-12 and the other with pages 1-13 because of an extra page having been added as page 4, they can be compared by specifying two page ranges, 1-12 for the first and 1-3, 5-13 for the second. This will make DiffPDF compare pages in the pairs (1, 1), (2, 2), (3, 3), (4, 5), (5, 6), and so on, to (12, 13).

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2  
This is the best I've seen. The only issue I see is that it compares the pdfs page-for-page. So if you add a paragraph on say, page 1, the beggining and end of every page after that does not match. :( – krumpelstiltskin May 8 '11 at 0:21
1  
I think the link is no longer correct. The new version 3.* seems to be available only for windows. The old version 2.* can still be installed via sudo apt-get install diffpdf, though. – peq Apr 9 '14 at 15:48
up vote 9 down vote accepted

I just figured out a hack to make DiffPDF (the program suggested by @qbi) usable for more than minor changes. What I do is concatenate all pages pdfs into a long scroll using pdfjam and then compare the scrolls. It works even when large sections are removed or inserted!

Here is a bash script that does the job:

#!/bin/bash
#
# Compare two PDF files.
# Dependencies:
#  - pdfinfo (xpdf)
#  - pdfjam  (texlive-extra-utils)
#  - diffpdf
#

MAX_HEIGHT=15840  #The maximum height of a page (in points), limited by pdfjam.

TMPFILE1=$(mktemp /tmp/XXXXXX.pdf)
TMPFILE2=$(mktemp /tmp/XXXXXX.pdf)

usage="usage: scrolldiff -h FILE1.pdf FILE2.pdf
  -h print this message

v0.0"

while getopts "h" OPTIONS ; do
    case ${OPTIONS} in
        h|-help) echo "${usage}"; exit;;
    esac
done
shift $(($OPTIND - 1))

if [ -z "$1" ] || [ -z "$2" ] || [ ! -f "$1" ] || [ ! -f "$2" ]
then
  echo "ERROR: input files do not exist."
  echo
  echo "$usage"
  exit
fi

    #Get the number of pages:
pages1=$( pdfinfo "$1" | grep 'Pages' - | awk '{print $2}' )
pages2=$( pdfinfo "$2" | grep 'Pages' - | awk '{print $2}' )
numpages=$pages2
if [[ $pages1 > $pages2 ]]
then
  numpages=$pages1
fi

     #Get the paper size:
width1=$( pdfinfo "$1" | grep 'Page size' | awk '{print $3}' )
height1=$( pdfinfo "$1" | grep 'Page size' | awk '{print $5}' )
width2=$( pdfinfo "$2" | grep 'Page size' | awk '{print $3}' )
height2=$( pdfinfo "$2" | grep 'Page size' | awk '{print $5}' )

if [ $(bc <<< "$width1 < $width2") -eq 1 ]
then
  width1=$width2
fi
if [ $(bc <<< "$height1 < $height2") -eq 1 ]
then
  height1=$height2
fi

height=$( echo "scale=2; $height1 * $numpages" | bc )
if [ $(bc <<< "$MAX_HEIGHT < $height") -eq 1 ]
then
  height=$MAX_HEIGHT
fi
papersize="${width1}pt,${height}pt"



    #Make the scrolls:
pdfj="pdfjam --nup 1x$numpages --papersize {${papersize}} --outfile"
$pdfj "$TMPFILE1" "$1"
$pdfj "$TMPFILE2" "$2"

diffpdf "$TMPFILE1" "$TMPFILE2"

rm -f $TMPFILE1 $TMPFILE2
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1  
I made your script whitespace-compatible and added unique tempfiles. I hope you don't mind. – Glutanimate May 19 '13 at 16:59
1  
Also fixed a small bug where the script would create an empty text file in the working directory. (remember to always use double brackets with if statements that use ">" and related operands.) – Glutanimate May 19 '13 at 17:10
1  
One last remark: This script will work fine only for DIN A4 sized documents. You will have to adjust the PAGEHEIGHT value to get it to work with smaller documents. I'm sure there's a way to automate this but don't know how atm. – Glutanimate May 19 '13 at 17:21
2  
Thanks for making the improvements @Glutanimate. I've added support for comparison of pdfs of arbitrary and differing sizes (as long as the pages within each pdf are of uniform size, that is). – krumpelstiltskin May 19 '13 at 20:11
    
saved to a gist for convenience gist.github.com/timabell/9616807b2fe3fa60f234 – Tim Abell Nov 17 '15 at 17:27

If you have 2-3 huge pdf (or epub or other formats, read below) files to compare , then it is possible to combine the power of:

  1. calibre (to convert your source to text)

  2. meld (to visually search for the differences between the text files)

  3. parallel (to use all your system cores to speed up)

Below script accept as input any of the following file formats: MOBI, LIT, PRC, EPUB, ODT, HTML, CBR, CBZ, RTF, TXT, PDF and LRS.

If not installed, then install meld, calibre and parallel:

#install packages
sudo apt-get -y install meld calibre parallel

To be able to execute the code from anywhere in your computer, save following code in a file named "diffepub" (with no extensions) inside directory "/usr/local/bin".

usage="
*** usage:

diffepub - compare text in two files. Valid format for input files are:
MOBI, LIT, PRC, EPUB, ODT, HTML, CBR, CBZ, RTF, TXT, PDF and LRS.

diffepub -h | FILE1 FILE2

-h print this message

Example:
diffepub my_file1.pdf my_file2.pdf
diffepub my_file1.epub my_file2.epub

v0.2 (added parallel and 3 files processing)
"

#parse command line options
while getopts "h" OPTIONS ; do
  case ${OPTIONS} in
    h|-help) echo "${usage}"; exit;;
  esac
done
shift $(($OPTIND - 1))

#check if first 2 command line arguments are files
if [ -z "$1" ] || [ -z "$2" ] || [ ! -f "$1" ] || [ ! -f "$2" ]
then
  echo "ERROR: input files do not exist."
  echo
  echo "$usage"
  exit
fi



#create temporary files (first & last 10 characters of
# input files w/o extension)
file1=`basename "$1" | sed -r -e '
s/\..*$//                     #strip file extension
s/(^.{1,10}).*(.{10})/\1__\2/ #take first-last 10 chars
s/$/_XXX.txt/                 #add tmp file extension
'`
TMPFILE1=$(mktemp --tmpdir "$file1")

file2=`basename "$2" | sed -r -e '
s/\..*$//                     #strip file extension
s/(^.{1,10}).*(.{10})/\1__\2/ #take first-last 10 chars
s/$/_XXX.txt/                 #add tmp file extension
'`
TMPFILE2=$(mktemp --tmpdir "$file2")

if [ "$#" -gt 2 ] 
then
  file3=`basename "$3" | sed -r -e '
  s/\..*$//                     #strip file extension
  s/(^.{1,10}).*(.{10})/\1__\2/ #take first-last 10 chars
  s/$/_XXX.txt/                 #add tmp file extension
  '`
  TMPFILE3=$(mktemp --tmpdir "$file3")
fi

#convert to txt and compare using meld
doit(){ #to solve __space__ between filenames and parallel
  ebook-convert $1
}
export -f doit
if [ "$#" -gt 2 ] 
then
  (parallel doit ::: "$1 $TMPFILE1" \
                     "$2 $TMPFILE2" \
                     "$3 $TMPFILE3" ) &&
  (meld "$TMPFILE1" "$TMPFILE2" "$TMPFILE3")
else
  (parallel doit ::: "$1 $TMPFILE1" \
                     "$2 $TMPFILE2" ) &&
  (meld "$TMPFILE1" "$TMPFILE2")
fi

Make sure the owner is your user and it has execution permissions:

sudo chown $USER:$USER /usr/local/bin/diffepub
sudo chmod 700 /usr/local/bin/diffepub

To test it, just type:

diffepub FILE1 FILE2

I test it to compare 2 revisions of a +1600 pages pdf and it works perfect. Because calibre is written using python for portability, it took 10 minutes to convert both files to text. Slow, but reliable.

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