Over the past 24 hours, several notable iPad apps were updated to include support for the new iPad’s retina display. PDF Expert, my favorite PDF reader/annotator on the iPad, also received a great new feature – Document Thumbnails. Now all files are shown as thumbnails and moving PDFs around (i.e into folders) can be done via simple drag ‘n drops. Another anticipated update came from Air Display, where turning on the “HiDPI mode” on your Mac OS Lion will essentially turn that new iPad into a gorgeous 2048 x 1536 secondary display for your iMac/Macbook. Check out the complete “what’s new” for these updated apps after the break.