Yes, and as soon as the flowers have finished is a good time to splt and repot. Size depends on how big the pot is and how crowded the plants appear to be.
All Primula seeds are best sown fresh, so as soon as you see the seed head beginning to split open then that is the time to take and sow them. Seed sowing compost, cover lightly with grit or whatever you use, keep moist and shady.
I have propergated primroses in a few weeks years ago and found that this way works.Carol Kline showed on gardeners world to take the seed pod after flowering while the seed is still green . She scraped off the sticky green seed layed it on top of a pot of damp seed compost. when I did some I then put a very fine covering of pearlite to barely cover the green seed . I cant remember if Carol did this with hers ,but I then , like Carol put a piece of tile over the top and left it outside. I was a bit apprehensive as when I have sown primrose/primula type seed before it has always said on the packet not to block of the light as light is needed to germinate .
BUT the seed germinated in a few weeks. It was a bit of messing about with the sticky seed but worth it !