Currently, the rotate page option only allows you to rotate in 90 degree increments. Recently I was marking up a drawing set that had a large portion of the building on a 45 degree angle. Consistently rotating markups becomes cumbersome, and some items (like hyperlinks) are not able to be rotated.
If you were able to rotate the document by 45 degrees (or any custom angle) while working inside it, you would gain a lot of efficiencies.