Not a fan of how Illustrator handles opening PDFs
So I can agree that the old way of opening up a page in a multi-page PDF, making an edit, hitting save and having the page re-insert isteslf in the PDF is over. Am I happy about it, no, but Adobe must have had their reasons.
And don't tell me Adobe is not a PDF editing tool. PDFs are created by both InDesign and Illustrator and there are times a quick edit is needed or the native files are not available. Illustrator is often the last resort to fix something in a PDF when all other options are exhausted.
What I wish Illustrator did was to create a new file name when opening a multi-page PDF. The dialog box even says "a new document will be created when opening a multi-page PDF". However I've noticed the document name stays the same, so then if you are working away editing the page, and accidentally hit save, you overwrite your entire multi-page PDF. Why not call it "Docucment 1" or something?
I may be missing something, but this is a bad UI and twice now I've overwritten my entire PDF because I hit save.