My New 6 Upper Porcelain Veneers Are Lower on One Side. Can They Be Filed Down to Match? (photo)

Your veneers can be adjusted slightly so that they are more even. You don't want to adjust them too much as this can weaken the porcelain and cause chipping in the future.

Veneers once delivered, sould have a fine tuning appointment to shape, contour and adjust the bite as needed. Veneers as any dental proceedure is a dynamic process and highly customized to that patient. I'm sure it can be fine tuned. 

The short answer is YES, they can be filed down to match the other side. However, the amount could be limited by your occlusion. You do not want to compromise the anterior guidance of how your lower jaw moves in relation to your upper. You do not want to compromise that for the long-term health and stability of your teeth.