Today I toiled my dress block, the one I drafted on illustrator. According to the program, the measurements are correct. What made me check is that the dress came out too big.
In case you came to this post by google and don't know about sewing, this dress is supposed to be close-fitting, not a semi-fitting sheath dress. It also ended up too long in the bodice so the bust darts are about 3cm too low! The armscyes are also too low so raising my arms lifts the whole dress.
What caused all this you may ask. Well, I printed "borderless". On the little print preview, I couldn't see a difference. Just to check, I printed out two test squares. Each measured 10cm x 10cm on Illustrator. These are the results:
As you can see, it adds 2.5mm onto 10cm. That's an automatic scale of 102.5%! Over the length of a dress this can make a big difference, going up by about half a dress size. When you're sewing close-fitting clothes, this is a paramount difference. I've learned my difference: do NOT print "borderless" in Adobe Illustrator.
I thought I'd better post about this for the benefit of everyone who has this trouble, not just sewers and pattern makers. I hope it has helped you as much as it will me. :)