printing on a home printer and checking for accuracy is a bad good idea, home printers are super inaccurate. Only printers that can do good 1:1's are high end large printers, even fancy photocopiers are trash.
If you dont have a super printer to use from a engineer or something, then your best bet is just to measure the shit out of what you are wanting to make, its not so bad with something like a manifold gasket because you can measure from every hole which can give you many points of reference. Plus if you are confident that all the ports/bolts are at the same height(ie level) then thats another thing that will help