I just replaced the dust and pollen filter in my 2012 A3. I took a few photos. Here's how to do it. No tools required...
except a trouble light and a vacuum cleaner.

1. Look up under the front of the passenger side foot well for two plastic thumbscrews. Remove the thumbscrews and pull the

foam piece out. It bends without cracking.

2. Find the plastic filter cover and depress the locking tab while sliding the cover to the right (away from the driver

side). Remove the cover.

3. Pull the old filter down and out. It will bend without breaking.

4. Vacuum out the debris that just fell out.

5. Install the new filter with the chamfered corner facing up and to the right (away from the driver side). It may take a

little trial and error to get it installed.

6. Slide the filter cover into the slots in the filter and into the filter housing. Slide it to the left to lock it in

place.

Thanks to all the other Audi owners who posted messages to help me figure this out.