Managing a large collection of PDF files

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http://askubuntu.com – I have a large collection of PDF files and am looking forward to an application that: Is easy to install (Available in repositories) Is portable (migration to other computer running linux or windows should be easy) Allows annotating and tagging/ categorizing the PDFs Allows searching the text of PDFs, metadata, annotations, tags, etc. Allows batch import of PDFs Also allows importing PDFs without requiring to copy the physical files Is preferably open-source Allows backing up of library on-line Any suggestions? Please mention if your suggestion does not have any features mentioned above. (HowTos)