Which software to modify a pdf file?

So, all you need to do is download Adobe Illustrator CS (CS2 is better!), rename your .PDF to .AI, and open it with Illustrator. Modify anything you want, texts, images, etc., then save it as .AI
Rename your .AI to .PDF, and there you have it, a real PDF modified with software from the same manufacturer.
Or even better, in Illustrator CS2, click on "save as..." and when you confirm "save", a window opens and you can check the option "create a PDF compatible file". So check it, and you're good to go.
Congratulations to ARTIK for his superb tip! (I slightly "cloned" what he wrote very well)
...and while we’re at it, for the daring ones, still in Illustrator CS2 (this software is "magical"!), you can directly generate a PDF page from a simple copy/paste in WORD into a new file! It's child's play.

Your solution:
https://www.commentcamarche.net/informatique/windows/185-afficher-les-extensions-et-les-fichiers-caches-sous-windows/#pour-afficher-les-extensions

Hello! I downloaded the demo version of Illustrator which is really great for editing .pdfs as you mentioned. However, we can only edit one page at a time, so I had to save each page of my document separately; how can I "reassemble" my new PDF document? Thanks in advance if you have any tips!

False to modify the file as we can do with a WORD file for example.

Your thing isn't working! Okay, my doc is on Paint, but what do I do? Paint only offers me to insert shapes, colors, or erase... I can't delete text and rewrite in its place...

Well, if you erase it and the file doesn't return to PDF, how do you take an image of the PDF file, your trick :)

You can write whatever you want, but tables are not very practical! And if you’re missing some fonts, you can add them to Windows.

You're welcome!!!