What is the best position for a French drain between a wall and a patio?
If you're going to pull up pavers to install a french drain, you might as well just pull up all the pavers and get the slope correct instead. 

A well laid patio should naturally shed water via its pitch. The ideal solution is to pull up the pavers, re-grade the base layer (should be sand directly under the pavers) and then lay it all back down...perhaps with a slightly exaggerated pitch this time. 

If you insist on a drain, I wouldn't bother with a french drain and instead consider a surface drain:



It'd be a lot easier to install.