Apptapp://package/com.latenitesoft.sketches

Well, pdfviewer app isn't great. And it is nearly impossible to view large pdfs in it. But builtin safari plugin works as its desktop brother. Why not to use it? Because safari "cannot open local files"...have to install apache webserver (can be found in installer.app), place your PDF documents into webserver folder and access them easily via safari (in my situation smth like 192.168.0.109/doc.PDF)