DOCX is a more modern version of the DOC text file format, which appeared in Microsoft Word 2007 from Microsoft. It takes its name from the full name of Microsoft Word Open XML Document. As in the previous version, DOCX format files contain not only textual information, but also tables, charts, images, and you can perform any formatting actions with the text. The main difference is that a DOCX text document is not a binary file, but a set of separate files (XML files, docProps, Word and _rels folders) in a ZIP compression package. This gives maximum file security without damaging or losing data.
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.