All those were single documents? Not one document with 25 pages?
Have you tried searching for the names with Spotlight?
I have finally found all of the pages, thank for your concern Monika. To answer your question, yes they were single pages and yes I did find some of them using spotlight. I did single pages because did´nt know how to set up a whole document, I asked for some help from a friend and I am working on improving my skills now. Thanks, once again.
You're welcome. Glad you could solve the issue.
Opening a PDF in Illustrator is difficult in itself. Let alone a multipage one.
This script is helpful: Re: Introducing: Open Multi-Page PDF win/mac
Still opening the PDF is not the ideal workflow and only advisable when it's either a PDF saved from Illustrator with "Illustrator editing capabilities" or there's no other file available.
In order to combine multiple artboards/pages rom multiple Illustrator files into one file, you will need to create additional artboards in your workfile and then copy the content from the other files into your workfile.
Also: when working on an Illustrator file and saving PDFs for your client, I would always save an AI file for editing purposes and the PDFs on top of it in order to send to the client or the printing service.
You might also combine multiple PDFs into one PDF using Acrobat. Combine or merge files into a single PDF, Adobe Acrobat DC