I am designing large posters for print...A2 size and bigger. I create my photoshop file as 594 x 420 mm, drag a jpeg image which 7.6MB onto the canvas, enlarge it to fit canvas, then drop a logo onto it. I save as a PDF for print, which then saves to be over 200MB, which is huge.
How do I design large images for print? If I design on a smaller canvas at 300DPI, can the printers then enlarge it without effecting the quality?
Or what else can I do? Most things I am designing (a4 print ad's) end up being 50-odd MB's, is it because of the images I am using or what?
If you're designing for print, you shouldn't be enlarging JPEGs anywhere. It defeats the purpose of having a high resolution image if you're just stretching out lower-resolution images and saving. Also, 200MB isn't that big for a large poster. All that extra pixel data has to go somewhere. I've worked with CD layouts that have been much bigger than that.
If you need to reduce the size for transferring to the printer, then you can flatten as many raster layers (flattening vector layers won't reduce file size much in most cases and could potentially increase file size) as possible.
Other than that, check that you're saving your PDFs with ZIP compression for images and you're not including unused/hidden layers. Artwork that is suitable for vector graphics should also be embedded as such.