Batch replace text in pdf file

Hi all

I need to translate several pdf files. I have the original strings and their translation in a excel table, so putting them in an array and loop trough that array is not an issue.

However, I have no clue how to find/replace a text in a pdf file. I've opened the pdf in a texteditor but was unable to find any of the strings... It seems that the pdf is encoded/encrypted/locked in some way.

Anyone has an idea?

Thanks