A long long time ago I put up a couple of posts about a couple of ways to use Aperture's easy to use but completely undocumented book layout tool for just about any book printing service. I guess all of a sudden these services have become far more popular and hence I have receive a bunch of questions specifically related to blurb.com and Aperture. Instead of trying to recap all of the information exchanged I am just going to give a couple of guidelines to help point people interested in this the right way.
Just to summarize, there are two general approaches to dealing with other 3rd party print services using Aperture. The first and really simple way is to using one of the PDF to image options in the book printing menu and then place those images of the actual pages using the services layout facilities such as Blurb's BookSmart. For a while this was the only way to do it with blurb.com. The other way was to print to a PDF of the correct specifications for the book service. So one - print from Aperture ending up with JPG or TIFF images of the pages or two - print from Aperture ending up with a PDF.
In both of these cases I suggested using a custom automator workflow added to the PDF services with Aperture so that you could control the specs. These are easy enough to create by copying the ones already there and modifying them with the Automator tool. The whats, wheres, and hows are detailed in one of the other posts in this series. Here are a couple of considerations when doing this.
First off both approaches need a custom book theme - unless you do not want precise layout within the services formats you need to be using a custom them with the correct page and margin dimensions. In most cases this means existing books using built-in Aperture book themes will not work. This is not always the case. Some books have a bunch of white space around all of the page edges and would be fine cropped somewhat. Get the page and margin dimensions from blurb or other service. One other thing you probably want to do for either approach is to set up the printer in the Aperture book printing dialog for borderless printing.
The next thing that you need to pay attention to is the specifications of the files you are sending. That is why I recommended the customized automator PDF workflows for either images or PDFs. The first thing is the color model and color profile. As of right now you will be much better making sure your images whether PDF or PDF to TIFF/JPG are sRGB. This is not the case for the default workflows included with Mac OS X and Aperture. For instance using the built-in PDF-X workflow the embedded image files will be Adobe RGB. Don't believe me? Check them out for yourself. Don't know how to check them ? - definitely use sRGB.
Here is why for all of you color management pro wanna-be's out there. Let's take blurb.com. Their entire production workflow and hardware is optimized for sRGB. Just look at the little color space diagram they give you in their help section. Blurb goes on to tell you that if you are sending RGB image files to send them sRGB, not Adobe RGB or ProPhoto, or, etc, etc. After that they state that if you really really really want to send them something else to make yourself feel better send them a very specific CMYK profile for the HP equipment they use. That means you need images in the CMYK color MODEL and then convert them to the CMYK profile that they supply. First off if you are using Aperture you not only don't have CMYK images you can't have them - Aperture does not do this. Second there is NO reason you would want to with the minor exception of already having an InDesign document and images already in CMYK that you already use to deal with real process color printing presses. That is the only reason in which case you have no reason to be trying to do this from Aperture.
Why am I so viciously adamant on this? Because I want to leave no room for misinterpretation that people working in Aperture or Photoshop or anything else for that matter that are not dealing with CMYK printing presses have no need to deal with CMYK color models. That and I want to leave no room for misinterpretation that your output from blurb.com will be NO BETTER going through creating and probably screwing up your images/files to CMYK. Stop worrying.