What is the general size of on-site recruitment posters? If it is made in PS, what mode is good and what resolution should be set?

From the job fair?

They are usually spray-painted, so the size doesn’t matter, as long as it’s eye-catching.

RGB mode is available, 100 is enough. Color inkjet printing does not require a high resolution

You can choose according to the opening number table, such as folio, quarto, or you can use A1 (841*594)\A2 size (larger than quarto)

However, remember that color inkjet printing and roll-up banners are charged per square meter, so you’d better ask about the price of inkjet printing first and then design the size you want