Leaflets come in all fancy shapes and sizes, from a standard A5 to a modern square, or even a complicated cut out.
It's not just sizes you have to choose from but paper weight and finish. I'd always go for a thicker leaflet for a tactile and
professional feel. You'll have the option of several finishes,
depending on which printer you choose. Such as gloss, matt, matt laminate, uncoated, recycled. For a standard leaflet, a matt finish is a great modern edge, add a laminate to that for longevity (harder to tear). Contact me for advice on an ideal set up and design for your leaflet.
I don't offer a printing service, but can help you navigate the minefield of paper weights, finishes and paper types! Starting with GSM. This is the weight / thickness of the paper. If your poster is going up inside for a couple of months, a light gram, like 130 - 150gsm is absolutly fine. If they are going up for a long time and could be at risk of wear and tear, go for a 300gsm.
Finish / Coating. For temporary posters, save costs and go for uncoated. For fancy looking ones, choose matt laminate (expensive but have a lovely finish) gloss, UV Matt, and soft touch lamination are also options. Type of paper. There is Silk (has a slight sheen), Gloss (shiny), Blueback (poster paper), Weatherproof vinyl (outside) and general uncoated (cheapest option usually).