I did this a couple of years ago for numbered vouchers on a dot-matrix printer using Reporting Services 2005. I won't pretend it was simple or easy, but it definitely can be done.
As the others have said, you're probably best to find a way to get your own "dummy" copies of the real certificates so that you can make cheap mistakes while getting 80% or 95% of the way to where you need to be.
The most important thing to realize is that the Visual Studio report designer and the report viewer do NOT render the layout exactly the same. Should they? Yes. Do they? No.
As a result, what you see on the screen has to be treated as input into the black box between you and the printer and tweaks need to be made to get it exactly right.
To that end, I found that it was actually much easier to ditch the Visual Studio designer altogether for the report and went straight to editing the RDL in a text/XML editor (even if it is, in fact, Visual Studio).
It's relatively straightforward to read and work with, and gives you the clearest visibility to do the kind of measurement-specific adjustments mentioned by other answers. You basically don't want anything to be autosized or you're going to get weird results.
You also want to make sure that you run tests with various lengths of each of the values. On my vouchers, the first draft looked horrible when a REALLY long company name showed up and wrapped, causing a bunch of other stuff to move.
The bottom line, though, is that can be done and has been done before. It's going to be tedious, but is possible. Good luck.