Off the top of my head, I do have one suggestion. If your scanner supports a "send to printer" function then you may be able to set it up with the
Bullzip PDF printer which is a virtual printer for Windows that generates PDF files. If you can get the scanner to print to the virtual PDF printer, then you should be all set.
As for being unable to search for "PDF" using the forum's built-in search tool, that's due to a restriction in place forbidding search terms with less than 4 characters. I'm not sure as to the reasoning behind this, but every forum I visit that uses Invision Power Board (like BC) has this restriction.