docx
DOCX is a well-known format for Microsoft Word documents.
Introduced from 2007 with the release of Microsoft Office 2007, the structure of this new Document format was changed from plain binary to a combination of XML and binary files.
Docx files can be opened with Word 2007 and lateral versions but not with the earlier versions of MS Word which support DOC file extensions.
pdf
Portable Document Format (PDF) is a type of document created by Adobe back in 1990s.
The purpose of this file format was to introduce a standard for representation of documents and other reference material in a format that is independent of application software, hardware as well as Operating System.
The PDF file format has full capability to contain information like text, images, hyperlinks, form-fields, rich media, digital signatures, attachments, metadata, Geospatial features and 3D objects in it that can become as part of source document.
In most of the cases, existing documents are converted to PDF rather than creating a new PDF from scratch.
But that doesn’t mean there are no software for creation or manipulation of PDF files.