Maximum Width of a PDF

Actually, the answer is not quite so simple.

The PDF specification does have a limit of what nominally appears to be 200"x200" for a page. However, beginning with PDF 1.6, there is a feature known as UserUnit within PDF that allows a scaling factor to be placed within a PDF file. The default value (i.e., if it isn't specified) for UserUnit is 1.0 corresponding to 1/72 of an inch. The actual PDF limitation is not 200" but rather 14,400 units corresponding to 200 x 72 units per inch.

At this point, no Adobe applications other than Acrobat do anything with UserUnit. However, if InDesign, Illustrator, and/or Photoshop chose to take advantage of the UserUnit feature for PDF 1.6 or later file generation, they could increase the page size limit to whatever they wanted. For example, setting UserUnit to 2 in a PDF file allows a maximum page size of 400"x400" and each unit within such a PDF file would be interpreted as 2/72 inch instead of 1/72 inch.

Bottom line, Acrobat fully supports very large page sizes via UserUnit. If you want access to such large page sizes, it is the applications (InDesign, Illustrator, and/or Photoshop) that need to take advantage of this. Submit the feature requests to those teams!

          - Dov