I like the fact that PDF is supported, but I have hundreds and hundreds of PDF documents. Adding them one by one is going to be impossible.
Please add a PDF importer, for example a dedicated folder in Dropbox that automatically generates a paper document. Or even an "add to paper" menu option from the Dropbox folder itself. Same applies to imagines and documents.
Of course to be truly useful the PDF content would have to be full searchable from the paper search menu.