doc The .doc filename extension is a native file extension used by the closed source document processing application Microsoft Office Word. Initially developed and used by Microsoft since 1983, the filename extension .doc continues to be supported natively even in the most recent iteration of the word processing application Microsoft Office Word 2013. The more recent .docx filename extension however was introduced by Microsoft in Office Word 2007, becoming the default filename extension. Documents to be saved in the .doc format are saved as Word 97, 2003 documents.
pdf The .pdf file format extension was developed by Adobe systems in 1993 as a means of presenting documents in a consistent manner across different platforms, hardware, operating systems, and applications. The format was not released as an open source document format until 2008, though minimal proprietary technologies still controlled by Adobe Systems exist in the format. Every .pdf document carries with it the necessary meta information required to properly reconstruct the text, fonts, and graphics used to produce the document. This ensures that documents will be viewed in exactly the same way the author intended regardless of the device used to open the document. From conception to date, Adobe Systems has continued to support the format adding features with every iteration of the standard including hardened algorithms for document encryption and privacy. Today, many freely available readers exist allowing you to open and view .pdf documents and create or convert other file formats such as .jpeg and .doc into .pdf documents.