How can I filter/sort a Drupal view in this way?
The easiest way I can think of you doing it since you have just three areas, is creating One block display with two attachments. 

The block contains one area with the most recent pdf, and the two attachment, would contain one area each with the most recent attachment, and link the attachments to the block display.

See Image of how to add an attachment


UPDATE

When you are using more than one diaplay and are adding a display you want to make sure at the top of the popup dialog you choose for this display, rather than all display. See image below