Help with cookbook from scans

Adding to what Try67 just wrote, I concur. 

However, as a published author, I'm assuming that all of these recipes are from books that are long past their copyright dates. If these are from sources where the current copyright is still in service, you are asking to be sued right, left, and center by all offending authors — even if you give these away for free. That last bit is important because if you do anything that impedes the sale of future copies of these sources, you are in violation. Getting recipes for free means you do not have to buy the book they came from, so you are impeding the sale of the book and you are in violation.

But, on the assumption that these are all from books that are long out of copyright, your desire to merge the three individual PDFs into one is easy to do in Acrobat. Everything else you want to do should not be done in Acrobat. 

Overall, the basic issue/problem is that Acrobat is NOT a page layout application. You state that you want to add artwork. That can be a major pain in Acrobat, but it's relatively easy to do in a Page Layout application like InDesign. Plus, you can create the TOC there.  

By the way, TOCs should NOT be ordered alphabetically but by order of appearance. The contents (at the end of a book) SHOULD be alphabetical (along with sublevels, e.g., Fish, then subentries: Cod, then Salmon, not Salmon, and then Cod).

Regarding scanning your content, you may wish to look through a blog I wrote a number of years ago for Adobe on how to get clean, searchable scans. 

https://community.adobe.com/t5/adobe-community-professionals/scanning-clean-searchable-pdfs/m-p/4785435?page=1#M89

If you have no experience with InDesign, I might suggest you plan on giving this to your friends for next Christmas. It sounds like you think this can all be automated while you stand back. That's not how this will work. This will take some time and love, and when you finish, all of those you give this to will cherish it. But it will not be this Christmas. Even if you had it ready to go now, no book printing service could have it ready by Christmas. That's a sad but real truth. 

Oh, one last comment: any professional printing company that looks at the content and realizes that the recipes are still under copyright will (or should) refuse to print this, making all your work for naught.

Good luck!

What kind of TOC did you create, and how did you create it?

Generally speaking, Acrobat is not suited for creating a TOC from scratch, although it can be done.

For example, if your file contains bookmarks then a script can be used to converted them to a TOC, even with clickable links. I've developed a (paid-for) tool that does just that:

https://www.try67.com/tool/acrobat-create-a-table-of-contents-toc-in-a-pdf-file-from-bookmarks

But doing it by hand will require quite a bit of work, especially if you have a lot of items to add.