EndNote, DEVONthink, Zotero, Mendeley, Citavi, BibDesk, Qiqqa, JabRef, Bookends, ReadCube Papers, EasyBib, PDF Stacks, MyBib, Bibliography.com, FoxTrot Professional Search, Peerlibrary, Reference Manager, BibSonomy, PDF Search, OutWit Hub, Weava, KBibTeX, Zenreader, Auratikum, BibMe, Bibtex Editor, I, Librarian, Biblioscape, RefWorks, UbikReader, bibus, TextCite, RefMe, Droideley, FingerPDF are some alternatives to Paperpile.