How to compare 2 pdf documents?

Question

Documentation

The customer sent a long contract, which took a lot of time to study. After studying the contract, I sent the customer several edits. He sent me a new version of the contract. The question is, are there any programs that compare multiple versions of a PDF document and underline different sentences or words?

Answer 1

On a good note, preliminary documents are sent in Word, with a history of edits.
Ask the customer to send in a different format

Answer 2

Compare text from common office files .

Answer 3

If you don't have Acrobat DC, you can try https://draftable.com/sravnenie-dokumentov for PDF comparison ,
better than some analogues.

Answer 4

pdf2text 1.pdf > 1.txt
pdf2text 2.pdf > 2.txt
diff 1.txt 2.txt

If there is only the text of the contract, then the letters are compared without problems.