I have hundreds of pdf's in nearly a hundred folders, all managed with BibDesk. Is there a pdf reader and annotation app for iPad that can directly access these folders (bypassing iTunes) and maintain the same folder structure? I found a few apps (iAnnotate, PDF expert, PDF Reader Pro, ReaddleDocs), but these cost all 5 to 10 dollar. It's a bit expensive to just try them all out. PDF expert seems to be a decent app, but I can't determine from the few available screenshots how it deals with the folder structure. Any suggestions?