If you're getting a timeout while doing a PDF export and the exported content is not too big then you probably hit a Paged.js bug. Paged.js is the JavaScript library we use to layout the exported content in print pages. You can overcome this by unchecking the Table of Contents, Header and Footer from the PDF Export Options modal and then triggering the export again. This time the export will be done without Paged.js, relying solely on the web browser, which shouldn't pose any problems. Of course, the downside is that you loose the Table of Contents, Header and Footer. Fortunately Paged.js is under active development so we hope its bugs will be fixed soon.