Why when I try to upload a .pdf document into adobe acrobat, I get a message that reads "Acrobat.com does not support converting .pdf files to PDF." This isn't making sense to me.
Not sure what you are doing here. Acrobat is an application that opens and creates PDF's. You don't "upload" anything in to it.
Now Acrobat.com is a different item (and this isn't the forum for it) but you can use it to create PDF's online but if it's already a PDF, you would get that message yes.