At least for cutting the plates it is a good idea. I think for those who, like me, are better with a keyboard than with a marker and a ruler, printing the outlines of the plates from a computer drawn document is a very good idea. I did that for my pedal brackets and I'm very happy with the result. I even regret I haven't thought about it before
The best thing is to print the shapes on a sticker (A4 non-cut label sheets are excellent), and to stick it on your metal plate. Then you just have to follow the outline. Cutting is still as easy/difficult, but at least, the outline you are following is right
For the tubes though, I don't think it is possible (except spending hours drawing each tube end)
Anyway Martinl, you can not really start from your PDF copy of the book, as it is just pictures of the pages (non-vectorial) and scaling them, without being totally impossible, will take a lot of time for each of it. You will need to re-draw the outlines yourself, or to find the CAD or SVG drawings which are scaled. PM me if you want more details about that, but as I said : I think this technique is OK for the plates, but if it is only for the tubes you want to use it, better use a mitre saw or buying a flat pack as the others members said
Hope this will help.
Bye.
Sylvain