How do PDF files work?. Nuance PDF Converter 6.0

How do PDF files work?

PDF files display texts correctly wherever they are viewed because they carry their typographic information with them. Fonts in the document are embedded in the PDF file and are used after distribution to reconstruct the document. The display does not depend on the needed font files being available on the viewing machine, nor on the language of its operating system.

PDF documents present their pages as images. They can be marked-up and commented, but the ability to change the basic text is limited. Most

PDF files can be searched, because the file has two layers. There is an image layer that is presented on-screen. Behind that there is usually a text layer that can be matched to the characters displayed on the screen.

Display layer

Text layer

When the starting point for a PDF file is a set of images, or a scanning process, this text layer is not present and the result is an image-only

PDF. When the starting point is an editable document, the text layer can be created and the PDF is called 'Normal' or 'Searchable'. The creator of a

PDF can require provision of a password to allow access the text layer.

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