The statement has been circulating online for some time that a file Single page PDF can cover approximately half the surface of an entire country like Europe. Specifically, the surface of our nation measures just over 300,000 km2; if you could print a single document PDF, you could produce a sheet 381 x 381 kilometers wide, or 145,161 km2. Where does this curious assertion come from? Also, does it depend on the format specifications or does it have to do with PDF file readers?
There is a trace of the limitation on Wikipedia, which in turn refers to the document PDF Reference of 2006, published on the Adobe website. According to PDF specifications (version 1.7), Adobe Acrobat imposes a size limit of 15 million by 15 million inches, equivalent to 381 x 381 kilometers. This restriction, introduced with PDF 1.6, is associated with version 7 of the Acrobat software. But what if we create a single page PDF document that exceeds these dimensions?
The structure of PDF documents
The structure Typical of a PDF file includes a version number, a list of objects representing various elements, a table xref for object references, a trailer with the document metadata and a pointer startxrefuseful for interacting with the contents of the table xref.
Alex Chan explains that, by arming yourself with a little patience, you can change the page size by intervening on the parameters /MediaBox e /UserUnit, contained in the PDF. The former allows you to set the size of each page, while the latter helps you adjust the scale.
Increasing both the values of /MediaBox what about /UserUnit, the page size can be significantly expanded. The maximum allowed by Acrobat, as we said, is 381 kilometers per side. Any values that exceed this limit are promptly ignored by the Adobe software.
While Acrobat imposes a limit on the size of PDFs, not all programs apply the same constraint. For example, the preview application on macOS ignore the setting of /UserUnit and allows values of /MediaBox practically unlimited. In a playful experiment, Chan created a PDF file with a width equivalent to distance between Earth and Moon.
Consider the example in the figure: the length of one side of the PDF document is slightly less than the distance that separates the earth’s surface from the lunar surface (384,400 km).
In unraveling the riddle of PDF size limitations, we discover that while Adobe Acrobat imposes restrictions (albeit very generous ones…), the broader world of PDFs presents a canvas with more flexibility and potential than you might think.
Opening image credit: iStock.com – 1xpert