Forwardable is a design constraint
A viral PDF generator helps you produce a file. The file still needs a job a second person can see in ten seconds. Checklists, one-pagers, and scorecards travel. Memoirs about your journey do not.
Put the source on the first page
Brand, URL, and what to do next. If they forward the PDF, you want the next reader to find you. That is the only honest "viral" mechanic left.
Do not lock the value behind a pitch
If page one is a pitch and the tips start on page eight, nobody forwards it. Teach first. The generator is formatting. You are the editor. The quiz asks whether this file is for a list, a forward, or a printout so the shape matches.