PDF is short for Portable Document Format, which can be translated from English as “Portable Document Format”. It was developed by Adobe Systems for use by US federal authorities as a tool for storing working documents. This is a universal cross-platform format, which is now standard for electronic documents. It serves to convert text files (including photographs or other images) into electronic documents without any loss. To read PDF files you need special programs - Adobe (Acrobat) Reader, PDF-Viewer and others.
DJVU is a raster image format that is used to store scanned magazines, books, catalogs, other types of printed matter, as well as simply scanned images. In addition, files of the specified format developed by LizardTech can be used for text documents in which there are many formulas, figures, diagrams. Other formats of similar functionality are not able to reflect all the details of such files so accurately. DJVU is the optimal format for creating electronic libraries in which there may be large volumes of files.