Krop
Krop – free and open source simple graphical tool to crop the pages of PDF files for Linux
Boomaga
Boomaga is a virtual printer for viewing a document before printing it out using the physical printer
PDFsam
PDFsam – free simple and open source cross platform software for splitting and merging PDF files
qpdfview
qpdfview – free and open source software for viewing PDF documents with tab support
Okular
Okular is a free and open source, multi-platform document viewer that supports a variety of formats
Evince
Evince is a free and open source program for viewing PDF documents, comic books, and others.
Сhoqok
Choqok is a free and open source microblogging client by the KDE community
Cawbird
Cawbird is a free and open source, modern and lightweight Twitter client
Makagiga
Makagiga is a free and open source multi-platform simple software for creating to-do lists, notes, and reading RSS feeds