The [PDF spec](http://www.adobe.com/devnet/pdf/pdf_reference_archive.html) includes an option to cause PDFs to open full screen when users open them. I'm a fan of the feature because it maximizes screen real estate and creates a simple, focused, experience for the PDF readers. Using this option is one of my two essential tips for creating an impactful newsletter targeted at being read online. The other tip is to use a "portrait" format document, to match the shape of most screens.
Many PDF viewers respond to PDFs that are set to open full screen, but a number of PDF generation tools don't provide you option to set this preference when creating PDFs. I ran into this with [Xournal](http://xournal.sourceforge.net/) which is a nice application for Linux-based tablets, but offers no PDF export options.
So I found a way to update a pre-existing PDF to set the preference to have it open full screen by default. The key here is that PDF is a text-based format, so preferences in it can be updated manually by opening and editing the file according to the PDF spec, or the same effect can be accomplished with automated tools. In this case, I found that I needed to update a line that started like this:
<< /Type /Catalog
After `/Catalog`, this is all that needed to be added:
I automated this with a simple script that I named `make-pdf-full-screen.sh`. It works for the simple case when no "PageMode" has been declared, as in the Xournal case. I don't expect it would update the PageMode properly if it was already declared. For a safer solution consider opening the PDF in a text editor to manually set "/PageMode /Fullscreen" on the initial `/Catalog` line. Alternatively, you could use a formal solution like [PDF::API3::Compat::API2](http://search.cpan.org/dist/PDF-API3/lib/PDF/API3/Compat/API2.pm) which appears to have the features needed to solve this with Perl.
Here's the contents of my little script to automate the update:
# usage: make-pdf-full-screen.sh file.pdf
# The file will be modified in place so that it opens full screen.
# The current approach is naive... it assumes no Initial View has been defined.
# by Mark Stosberg
perl -pi -e 's?<< /Type /Catalog?<< /Type /Catalog /PageMode /FullScreen?' $1