Is there a PDF size limit?

There are maximums, but it is not 10,000 pages. It is larger. But the problem with large documents formed from scans is that you may be taxing your system. Why do you feel the need to have a 10,000+ page document. Especially, one that consists of scans. With scans unless you have ocr'd the documents you cannot search the contents. You can setup a table of contents pdf and use links to get from one document to another. If you are running into corruption problems, you loose the entire document. If you have smaller files, then if corruption occurs you can restore the smallest part from backup or regenerate as needed.

There's no explicit page number limit but there is a limit on indirect objects of 8,388,607 in a 32-bit PDF rendering application - Acrobat and Adobe Reader are both 32-bit code - and because each page consumes at least one indirect object, every PDF file created by or opened by Acrobat must have less pages than that. If you were to create a native x64 PDF application you could add more pages, but the resulting files wouldn't open at all in 32-bit apps.

Architecturally there is only one limit in the PDF standard: the overall file size must be below ~10GB as the cross-reference tables which define the PDF structure use 10 bits.

When you get to extremely large sizes, you limit the usefulness of the document. You might be the only one with enough memory and harddisk space to open the thing. So the practical answer is much lower than the limit in terms of size. The limit is in useful content and ease of use. It is a lot simpler to create a sequence of PDFs and link them. For a book, it might be by chapter. For archived documents, it might be by month or such. In any case, a huge document becomes useless fast, even if it is technically possible to make it that large.