I asked iStudio about the kinds of pdfs it generates and information about image quality and color control. The following is their long response:
----From iStudio----
At present, iStudio Publisher creates PDF files using Mac OS X's
inbuilt services. It provides no specific options or settings for PDF
processing, although you can add your own PDF processing using Mac OS
X's Quartz filters. We are considering adding support for PDF settings
in the future. That's not to say iStudio Publisher creates poor
quality PDFs, and in fact we've made several design choices about the
PDF creation process that results in PDFs suitable for high quality
printing.
Images are embedded in iStudio Publisher document (.ispx) files in
their original formats. Exporting a PDF also embeds the images in the
PDF file at their original resolution and compression level, so
there's no loss of image quality.
iStudio Publisher can be used as part of a colour-managed workflow.
Document images and other coloured document artifacts (lines, fills,
text, etc) are all tagged with ICC colour profiles, which are stored
in iStudio Publisher document files and are transferred to the PDF.
ICC colour profiles can be changed during document editing. Some
printers may require colors to be set to CMYK at document edit time.
For more information about setting CMYK colours, please see the
iStudio Publisher Help page "CMYK colors".
iStudio Publisher creates PDF files with font subsets embedded, which
ensures all font information remains available to remote viewers even
if they don't have all of your document's fonts installed on their
computer. Embedding font subsets involves only including the
individual font glyphs (characters) that are actually used in your
document rather than embedding complete fonts en masse; it helps to
minimize the PDF file size. iStudio Publisher controls and sets the
position of each and every character in the PDF rather than relying on
the use of default PDF layout algorithms, so you can also be sure your
page layout will be faithfully reproduced.
Something else we've just added that may be of interest is a page
imposition booklet printing solution that's described here:
http://www.istudiopublisher.com/index.php/support/istudio-publisher-frequently-a sked-questions#section3_question7
