Been researching this for a few hours now and stumbled across your interesting article.

My problem simply is:
When exporting my 100 pts x 100 pts InDesign document to PDF, the PDF at 100% takes up 136 x 136 pixels on screen.

…perhaps dispelling the myth that 1 points = 1 pixel.

What’s interesting is that when I export to JPEG, the JPEG at 100% take up 100 x 100 pixels on screen. This is correct.

There are NO images placed in my InDesign file.

Your thoughts on this would be greatly appreciated.

Please email me if you reply! (unless I’m automatically notified

Thanks for the comment. You are right, it would be a solution, but 1000pts in InDesign is really big. That won’t be such a problem either, if you are working purely digital. The problem comes with printing. If you are going to produce a paper interaction design document, pages 1000pts in width are a bit cumbersome. Of course, you could always scale the whole thing back again.

If you want your site to be 1000px wide then why not just create a InDesign file that is 1000pt wide?

Exporting a 1000pt document as a JPEG from InDesign gives you a 1000px file in P/Shop.
Wouldn’t this do away with the font size conversion formula, allowing you to design in pt sizes knowing that they will display the same as their px equivalents?