Skip to main content

Portable Document Format (PDF) is an open standard for electronic document exchange maintained by the International Organization for Standardization (ISO). Questions can be about creating, reading, editing PDFs using different languages.

The official ISO Specification (ISO 32000-1, a.k.a. 'PDF-1.7') is important as a reference, but it is not exactly written for PDF beginners.

Beginners may start with these two easy-to-read resources:

Information Extraction

Extracting text from a PDF may not be possible without resorting to Optical Character Recognition (OCR). Letters can be encoded as font glyphs, line art, vector graphics, or raster images.

PDF files generally contain drawing instructions. There's no such thing as "a table" in most PDF files. There are lines, glyphs, and raster images (and clipping, and color spaces, and so forth). It is all but impossible to determine what is or isn't a table in an arbitrary PDF file.

Note that a glyph is not a character. A glyph has an appearance; whereas, a character has meaning. Each font in a PDF may or may not map it's glyphs to characters.

If at all possible, use the source data to extract information, rather than relying on the PDF. This file format is designed for visual consistency, and very little useful normalized data can be extracted from its contents.


A PDF file is often a combination of vector graphics, text, and bitmap graphics. The basic types of content in a PDF are:

  • text stored as content streams (i.e. not text)
  • vector graphics for illustrations and designs that consist of shapes and lines
  • raster graphics for photographs and other types of image

Related Links

For additional information about this file format see: