Review comments on PDF20

The PDF Technology Notes link is broken. (I assume this is broken on all the
PDF techniques and should be fixed everywhere.)

Assistive technology should be lower case (e.g. "recognized by assistive
technology").

I suggested modifying the alt text for the first image to be "A correctly
marked up table in Word, with complex headers, before conversion to PDF."

There is a formatting problem with list item 2, where the line breaks
instead of wrapping, turning it into a new paragraph and messing up the
numbering on the next list item.


In the test procedure, change "For each table" to "For a table"