What are PDF Units and Coordinates?

Before working with headers, text, or form fields, you should understand the PDF coordinate system.

PDF Units

Space in a PDF file, also known as user space, is measured in PDF units. The PDF specification defines PDF units as 72 PDF units to 1 inch.

For example: an 8 1/2" x 11" piece of paper converts to 612 PDF units by 792 PDF units.

Origin and Positioning

The PDF specification places the origin (0, 0) of a PDF document in the lower-left corner, with y increasing upward and x increasing to the right.

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