Poppler is librarified PDF rendering toolkit derived from the Xpdf 3.0 code base. It can utilize X11-independent rendering backends like Cairo, Splash, or Qt4 Arthur. It's not designed for platform-agnosticy, but proper BSD/Linux integration; is used by various PDF applications (Evince, Okular, TeXStudio, pdftotext, Zathura, Xournal, Inkscape), and comes with a set of command-line tools of its own.
OCRmyPDF adds an invisible text layer to PDF documents after passing it through the Tesseract OCR engine. The output will be PDF/A with a selectable but invisible text layer above scanned image-documents. This allows later searching and archiving.
Evince is a document viewer for multiple document formats. The goal of evince is to replace the multiple document viewers that exist on the GNOME Desktop with a single simple application. Evince is specifically designed to support the file following formats: PDF, Postscript, djvu, tiff, dvi, XPS, SyncTex support with gedit, comics books (cbr,cbz,cb7 and cbt). For a comprehensive list of formats supported, see Supported Document Formats.
Xpdf is a free and open-source PDF viewer for operating systems supported by the Qt toolkit. Versions prior to 4.00 were written for the X Window System and Motif. Xpdf runs on nearly any Unix-like operating system, but binaries are also available for Windows. Xpdf can decode LZW and read encrypted PDFs. The official version obeys the DRM restrictions of PDF files, which can prevent copying, printing, or converting some PDF files. There are patches that make Xpdf ignore these DRM re
wkhtmltoimage and wkhtmltopdf render HTML pages into PDF or convert them into image files respectively. They're utilizing the QT Webkit runtime for "headless" operation without a running browser or display server.
Texmaker is a free, modern and cross-platform LaTeX editor for Linux, MacOS X and Windows systems that integrates many tools needed to develop documents with LaTeX. It includes unicode support, spell checking, auto-completion, code folding and a built-in pdf viewer with synctex support and continuous view mode. Texmaker is easy to use and to configure.
FlaxPDF is a fast, nice multithreaded PDF viewer for the desktop. As long as there are more pages than cores, every core will get a workout. Light on dependencies, trimming borders, and aggressive caching are its major points.
TEBookConverter is an easy to use ebook converter for Windows. It utilizes Calibre. Supported input formats therefore are cbz, cbr, cbc, chm, djvu, docx, epub, fb2, html, htmlz, lit, lrf, mobi, odt, pdf, prc, pdb, pml, rb, rtf, snb, tcr, txt, txtz. Supported output formats are azw3, epub, fb2, oeb, lit, lrf, mobi, htmlz, pdb, pml, rb, pdf, rtf, snb, tcr, txt, txtz. It provides a speedy conversion process due to being multi-threaded.
pdfgrep is a commandline tool to search through PDF files. It's similar in its application to grep, and also allows searching with regular expressions or case-insensitively, and recursively through directories. It prints out filenames, page numbers, number of occurences, and most importantly a colorized match list.