" 5, File->Export to PDF;
" Please note the step 5 is vital. Selecting File->Print, followed by choosing "Print to PDF", may not keep the scaling.
Yes, that should work well. --
But I didn't see why that'd be a problem for me -- Here's why it was...
My "oversized" 12" x 12" drawing - a router template, that was arranged so that only the center section would print on US Letter size paper, was getting reduced a touch. Even when I carefully tweaked the scale to enlarge it a touch.
I'm using LibreCad on a Linux platform, and it took a while to figure out that in my printer properties there was an option ticked that "scaled to fit" anything that exceeded the page size if it didn't already contain scaling data. ( such as the 1:1 printout)
The image being sent was the 8.5 x 11 inch image, but the printer driver scaled that for the minimum margin (.2 inch in x,y).
Now with that box un-ticked, I get my expected 1:1.
By exporting to PDF then printing that PDF file, the PDFdriver probably would have bypassed that issue - but as mentioned a direct "Print to PDF" probably would have auto-scaled also.