Why can't I export my report to pdf?
There are a number of reasons PDFs from reports can crash.  It's usually a matter of running out of memory, but that's not exclusively a hosting problem.  If you have a really big report with tons of pages and tons of columns, that can cause problems when a 4- or 5-page report displays easily.  Remember: when you view the report, you're only seeing one page's worth; when you're sending it to PDF, you're rendering all the pages at once.

You should probably try installing wkhtmltopdf, which runs a headless WebKit on your server to generate a PDF.  CiviCRM has built-in support for it; it's just not the default because it doesn't assume you can install additional software on the server.

Once you've installed it (there's a package for Debian wheezy), just go in CiviCRM to Administer > System Settings > Misc and tell it where to find wkhtmltopdf on your system.