Death, taxes and PDAs. Yep, including public displays of affection as one of the few constants in life. As long as people are in love and we do not live in hiding, there will be a common love. PDA can be totally acceptable. Adorable, even. But it is a slippery slope that can be repulsive and completely inappropriate. Here is a brief summary of yes and nos.
Ask your partner
It is possible that your partner may feel uncomfortable with things that are not even eligible for the PDA. How to make an assumption about the comfort level of your partner is not the best of ways. It is always best to start a discussion with your partner to be clear about the conditions and actions that could hurt you at ease.
Acceptable: link arm, grip and steady fingers intertwined.
Too much: give the other a "job arm" aka rubbing her almost all giving a massage arm. It can be considered the "working arm" because it looks a bit like what happens below the waist with his hands. In addition, arms swinging back and forth could be troublesome for people walking and stretching your arms too far. Basically, do not forget to be spatially aware.
Yes: Stolen Kisses
A kiss the forehead kiss here or there? Yes, go ahead.
No: Kissing Language
This is where the language belongs when you are in public - in the mouth. His own mouth. There never was a time when kissing in French public is appropriate. Even in France. Probably even more particularly in France.