PDF is a file format developed by Adobe Systems for representing documents in a manner that is separate from the original operating system, application or hardware from where it was originally created. A PDF file can be any length, contain any number of fonts and images and is designed to enable the creation and transfer of printer-ready output.
Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images and 2D vector graphics that compose the document. They do not encode information that is specific to the application software, hardware, or operating system used to create or view the document.
The .txt file extension is one of the most ubiquitous file types. The file generally consists of plain text only and contains no formatting. Almost any application that can handle text can open a .txt file. As a result this format remains popular due to its support across all platforms and Operating Systems. The file type is one of the oldest file types in existence with its origins tracing back to the first computers.
A .txt file normally uses a basic character set which contains letters, numbers and symbols. A typical example of this would be the ASCII character set. The main alternative to ASCII is Unicode. Unicode is a rival format for text files. A plain text file should only contain several non-printable charaters such as new lines, tab and form feed.