Try and obtain the original layout(source file). There are always problems when trying to edit a PDF in Illustrator.
If you cannot obtain the source file:
Instead of opening the PDF with Adobe Illustrator:
Step1: Create a new file in Adobe Illustrator with the same dimensions as the origial PDF
Step 2: Go to: File > Place and select your PDF file, place page one.
Stept 2.1: note: After you have place the PDF file you might need to Embed it;(Embed button is in the Tool Option pannel that is bellow the Main Menu).
Step 3: Go to: Window > Artboards > Create New Artboard
Step 4: On your new artboard repeat step 2 but place the 2nd page in the PDF
Step 5: Repeat step 2 and 3 and 4 untill you have placed(and embeded) the whole PDF in Illustrator.
note: not recommended for file with more than 20 pages, it will work but Illustrator might crash, so save every 2 min :)
Try to edit the PDF with Adobe Acrobat, not with Illustrator. link: http://www.adobe.com/products/acrobat.html
*note: not Acrobat Reader, Adobe Acrobat, the full software, its not the free version.
There is a great add on for Adobe InDesign that lets you import PDF's to InDesign:
So instead of using Illustrator to edit your PDF you would use InDesign, and also add the plugin above, you will then use the plugin to import the PDF to InDesign, it works like magic sometimes, I have used it myself after @Alan Gilberson told me about it.