Portable Document Format (PDF) is a file format used to present documents in a manner independent of application software, hardware, and operating systems. The Specification refers to the specification that it needs to meet.
PDF file specification
In theory this is a really easy question to answer for non-Compressed PDF files. There is a reference table to all the PDF objects... What are subsetted fonts? Subsetted fonts are fonts which only include certain values. If you look at the fonts on your Computer you will... 
