I wish to share how I solved a problem and hope Aperture will fix it soon ;-)
Till about 15 days ago I could sync no prob projects with images and pdfs from Aperture to iPad and this for me is very important since need these pdfs with the images. Then suddenly it became impossible, iTunes simply could not see the new pdfs first then any pdfs present in Aperture.
I have all updated, cleared the ipod caches in aperture library, repaired permissions and DB in Aperture Library first aid, deleted and regenerated previews of the projects in which I was having problems … but nothing changed.
Then I solved the problem “simply” by making a small modification in each pdf file in my aperture projects (for example brighter). All of a sudden iTunes could see all the modified pdfs and import them without an problem into iPad2 and iPhone4S.
I hope they fix this with next update in Apple and in Aperture.
Also this: even if I do not select faces to sync in iTunes they are nevertheless all synced to my devices.
I hope above helps.