The physical limit of the database is imposed by an 2GB maximum file size of any of the database files, and that size is, for the database files that grows larger, imposed by the amount of the metadata of the indexed PDFs.
I currently have a test database with more than 250'000 indexed PDFs, with some very larger custom metadata fields (to test some things) and the bigger database file is only 250MB (and this is much bigger than what happens in a normal scenario, because of these dummy filed custom fields), so 100'000 is peanuts.
But for that amount of files, be sure to use a good directory hierarchy. Don't put all these PDFs is the same directory, or you are going to have problems with the Windows Shell itself.
