Some customers experience problems using Mac’s iPages PDF export when using professional printers.

Workaround is a solution which may be useful in this case.

‘(…)When you’re ready to save your Pages document, avoid the temptation to use the Export or Print command to save your file as a PDF. Instead, if you’re running a version of the Mac OS X prior to Tiger, choose File > Print. In the sheet that appears choose Output Options from the third pop-up menu and then PostScript from the Format pop-up menu that appears. Click Save to dismiss this window and then Save again to Save the file. If you’re running Tiger select File > Print and in the resulting sheet click the PDF button, choose Save PDF as PostScript command, and click the Print button.

Now that you have a PostScript file, open it in Preview, where it will be converted to a PDF file. Once there, chose File > Save As and save the file. Although this may seem like you’re unnecessarily going over the same ground twice, saving the file as a PostScript document and then converting it to a PDF within Preview makes the file behave properly in Acrobat. When I did this, the shadows that appeared in Pages and Preview finally made their way to Acrobat as well.’
www.macworld.com/article/44923/2005/05/pagespdf.html