1. They're both correct and have basically the same meaning, but I think the most natural, simple way to say it is: "I remember you working on that." 2. I'll try to explain the precise meaning of each one. "I remember having seen this document before." This means that in the past, I remember looking at this document and knowing that it was a document that I saw previously. "I remember seeing this document before." This means that I look at the document now, and I remember seeing it in the past. I hope that's easy to understand!

your? ---> you're (you are) ---?---> you were