Why can't I add an attachment like a PDF file?

[Rallymaster]

Early on, members used this feature to post photos. It was not meant for that, but it was easy so that's what some members did. The allocation got filled up and if I increase it, I'd have to pay more money to Proboards. And then it would fill up again and we'd have the same problem.

I COULD delete all posts with attachments, but I don't think I want to do that. So for now, no attachments.