This tip could just as easily go under the Create Forums since it involves Create's exporting functions, though it's not necessary I guess. My tip isn't always very useful, but there are occasions.
I just did my portfolio, and I had a lot of raster images with transparency overlaid onto gradients and other elements behind them. While Create, PStill, Mac OS X and consequently any printer you can buy yourself can handle transparency in PDFs, your average Kinko's (by "average Kinko's" I mean the typically well-below-average Kinko's, but I repeat myself) uses something like Acrobat 4 to read and print PDFs. Even my local real printer hesitates to accept PDFs, especially if they have transparency. One solution is to simply export your layouts as TIFF files, and this is often fine. However, there are times when you really want to have the same crisp vectors (lines, shapes, fonts) that a PDF or EPS file provides.
Here's my tip for keeping the transparency effect while keeping the rest of your vector work otherwise in top shape. What you''re basically doing is converting only a part of the document into TIFF format instead of the whole thing. Again, it's overkill often enough, but just in case…
1. Select the transparent graphic and its background (if it's a page background, then don't select anything on the page).
2. Drag a high-res TIFF out of the image well to your desktop or export the document as a TIFF to wherever you can access it again quickly, like your desktop.
3. Re-import the image back into a copy of your document. (Great use for Exposé here.) You can either crop the image in PhotoToWeb first or create a mask group in Create to isolate the area or item that required transparency. Move the cropped image into place in the document.
4. Now you can export or print the resulting document (you saved with a new name, right?) as a PDF, preserving lines, shapes and fonts otherwise. If you're bringing this to a real printer, repurpose the file with PStill with the Prepress settings. The document should be compatible with Acrobat 4 and QXP. If they're still worried they might not take the document, you can normalize it as an EPS in PStill instead, which they should gladly accept.
Something I noticed when testing this tip: image files like PNGs and TIFFs that have transparency retain their transparency in PDF files even when you tell PStill not to preserve transparency and save it to the PDF 1.3 spec. Preview didn't like the normalized .eps and .ps files of the file, so I don't know if it's true of those file types as well.
PPS: I should also mention that TIFFany does an excellent job of removing an image's background so I can overlay things like scanned pencil sketches onto other things like renderings.