Yes. And you might want to change your documents to CMYK too. Your text and vector elements will be preserved (read: sharp), so use that when you can. Once you rasterize your text, the result will be a bit 'soft', no sharp borders, because the anti-aliasing translates to in-between pixels. So if you do lay-outs in Photoshop, try as much vectors as you can (also for boxes and lines) and save as pdf. If everything is just pixels, you might as well save as .tif file (and use LZW compression), that's a lossless file format used a lot for graphic files. I don't know about adding to a pdf without Acrobat. You can open it again in Photoshop, but in the long run, even at maximum setting, you will get jpg artefacts, because it keeps being re-compressed. By the way, I really would not recommend creating lay-outs in Photoshop if anybody asked. I asume you do not have Illustrator or InDesign? Especially the text could suffer, because the way PS handles it is not on par with programs that are made for that. But I understand you are already in the process, so good luck with that! Oh. And you have to work at 300 dpi ofcourse...