Best file format for PS and Illustrator files to be placed into ID

Question

I'm writing a proposal using InDesign. It will be output to PDF for circulation among the team members; I imagine they will view it on a variety of screens and some will print it out on various desktop printers.
I have a variety of images, all in color, done in InDesign, Photoshop and Illustrator that need to be placed into the propsal. Sizes range from 5x7 to 2x2. Some are quite complex with fine detail.
I've just viewed the proposal in ID Overprint Preview / High Quality Display. The images don't look great. Lots of ragged lines.
I usually save everything to JPEG with a quality of 80-90...but that is just a habit, I have no reason or justification for this practice.
I'm wondering if I should go back into the original ID, PS and AI files and resave them as something else before and then place them again.
Does anyone have any recommmendations or thoughts to offer?
I'm using CS4 on a MAC. My computer is a little bit underpowered for the project at hand, but I'm willing to put up with a bit of slow performance and lag if it results in a better end product.

Answer 1

Jagged lines is a hallmark of low resolution, not file type, or a lower quality screen preview than you think you are using. Check the Display performace settings again to be sure they really are correct, and if they're set to allow object level settings, you'll need to verify that each object is also set correctly.
Beond that, saving as .jpeg is always destructive. For the web, that's fine, but for print you should never use anything, in my opinion, but the highest quality settings for saving jpegs, and I advise again using jpeg at all. If you image is all raster data (pixels) save as .psd or .tif. If it has live type or other vector content, save as Photoshop PDF. In Illustrator save as .ai or PDF with Illustrator editing capability. If you change the extension of the Photoshop PDFs to PDP they will open in Photoshop instead of Acrobat when you use Edit Original.
As I said, the jaggies are a hallmark of low resolution. We often have people tell us that the file is 300 ppi, but it turns out that's at some very small dimension and the imaga has been scaled up in ID. Both the Links panel and Info panel can show you the resolution information for your images. There will be two numbers, actual and effective. Effective resolution is the only number that matters. For printing on a desktop printer I like to see a minimum of 150 ppi, but you might get away with as low as 90 for a non-critical image. For press 300 ppi would be the rule of thumb, and dropping below 200 is asking for trouble.
How the file looks in ID is not nearly as informative as how a PDF exported from the file looks, or prints. For a high-res image in ID you are still looking at a lower resolution screen preview, not the actual image as it will be output. Export settings that downsample too far or apply too much compression to reduce file size can also turn a good document into a clunker.