As the title suggest, I am trying to allow my users to upload documents on the forum. Are there any plugins to do so, or is this something I will have to implement myself? Thanks for your patience.
You could allow local uploading and specify a file size, go to Settings > Post > Tick Allow Users to Upload Regular Files, then adjust the file size from the default 2mb to whatever you feel you need.
This will give you a new icon on the composer. I've just tested it with a pdf and it works fine.