It’s not that complicated by it is kind of hard to write.
Basically you import your pdf.
Measure one line/gap whatever you’re trying to scale to a known size. Let’s assume it’s a simple square that you know you want to be exactly 0.75” on a side.
You measure that square using the ruler tool and find that it’s actually 1.17”.
Ok great now you know what your scaling factor is.
Select everything. Be sure the aspect ratio lock icon is selected.
You’ll see a width and height that reflects the entire svg size. Whatever is in either the width or height box add “* 0.75 / 1.17”. Hit enter and your entire svg will rescale.
When you measure the square now it should be pretty much 0.75”. You might see a difference of a couple thousandths due to rounding errors but you will be pretty much all set.
Make sense?