What does "fixed format" mean?

Starting in Office 2007, it is possi开发者_如何学Goble to save documents in PDF or XPS format. This is done (programmatically) by calling the method ExportAsFixedFormat. Googling has not turned up any definition of "fixed format" that seems compatible with what I know about the PDF file format. Is there a widely-accepted definition of this term?

Fixed format means that the document isn't editable.

When you save it as PDF or XPS it's an export to a format that is only intended for viewing.

(They are of course still editable if you happen to have the right software. For PDF for example that would be Adobe Acrobat Professional, i.e. not the free Adobe Reader.)

It probably means that these formats do not have formulas or layout engines.
In other words, your values, data, and layout are fixed.

CSV would also fit this definition, but it predated the feature.