Here is a technique using XML export resulted Excel format Re: Updated Version FMP2XLS v1.03 (export custom Excel spreadsheets)
You can arrange this technique to SVG format, it is XML image file. (But this would be some work)
There may be some screen capture way to do it or something like that. But what I would do instead would be to create an invoice from FileMaker that is HTML/CSS formatted and use a SMTP plugin on the server and PSoS to send a nicely formatted HTML/CSS invoice email. It assumes your clients can read HTML email, which most can now. But that is just as much of an assumption as if everyone can read PDF. Then again, assuming someone can read a JPG screen capture is an assumption too.
both ideas from u and t, above has given me the idea to test an Export (as html) this document can be _attached to HTML and may give you something usable. If not you can calculate the HTML and export that, then use as an attachment. It should be "clickable" or "viewable" even if the email is not html-formatted itself. Remember this would be an HTML document that is an attachment to the body of the email.
YMMV or YKMV
You could also create .rtf output using calculations. That should work pretty well. I've done this, not a piece of cake to program, but it is very reliable.