Mazie had the same problem when she was younger - most of the time when I wanted play time to end, she would jump at my knees and thighs and nip at me. I too have some ruined pajama bottoms and pants
!
What worked for me was to get her into a sit when I wanted to leave her penned area (she didn't stay too long at that age), and I could see in her face when she was anticipating a jump. I stated rather firmly "Don't" and stood perfectly still until I thought she was able to leave me alone. If I kept moving or tried to get away, she would think I was still playing with her. It took some patience on my part, but it really didn't take her too long to get it.
Lisa