How to diff PDF files?

Question

Sometimes, when I download a PDF file, such as one of my statements from my bank's website, and then, at a later time, download the same file again, both files differ.

How can I see how they differ?

I've tried:

diff file-1.pdf file-2.pdf

But that just prints:

Binary files file-1.pdf and file-2.pdf differ

Answer 1

Try:

diff -a file-1.pdf file-2.pdf | less

Or:

git diff -a file-1.pdf file-2.pdf

Example of diff's output:

1869,1870c1869,1870
< /CreationDate (D:20220504152530-00'00')
< /ModDate (D:20220504152530-00'00')
---
> /CreationDate (D:20220509154833-00'00')
> /ModDate (D:20220509154833-00'00')

Notes:

• For either diff or git-diff, the -a, --text option "treat[s] all files as text". (See man diff or man git-diff.)
• I use less in case diff -a outputs any binary data. (See this question and this comment.)
• You must add the --no-index option after git diff -a when you run the command in a working tree controlled by Git and both files are inside that working tree. (See man git-diff.)
• To view a PDF file's data as text, do less file.pdf.