IMHO, any document which supports your case should be uploaded.
Once i read somewhere, in the blogs/forums, when i was learning about the process, 'Chances of an application being rejected because of a lot of documents uploaded is none. On the contrary it may happen that if a certain document is missed, you may be asked for it.'
Even i have uploaded as many as i could which supported the case, including my Original Birth Certificate and a Notarised English Translation.
However for my case, it was not required, but i did't take chances, had asked someone (a friend of friend) who got a PPR, he said he had uploaded it, so I thought of doing the same.