Error when trying to export a multipage document from Excel (2011) with both landscape and portrait pages as a PDF file
This appears to be a limitation of the PDF generator within OSX itself. It appears as though the behavior has been present in OSX versions 10.5 Leopard, 10.6 Snow Leopard, 10.7 Lion and 10.8 Mountain Lion. According to posts within the Microsoft Excel 2011 support pages (here, here and here) when you initiate the print to PDF command from within Excel 2011 the program hands off the actual generation of said PDF to the operating system. On the surface it appears as though OSX is interpreting the page orientations differently and outputting as separate PDF files. I checked through the known issues with Microsoft Excel 2011 to see if there is an outstanding bug for this behavior but nothing seems readily apparent. The support pages contain references to different methodologies to get around the problem such as:


Automator workflows
VBA Scripts
Combing the resulting PDF documents within Preview
3rd party software to perform the actual generation (Adobe
Acrobat, PDFwriter, etc..)


The information available reports varying degrees of success depending on what solution you ultimately end up choosing. All the solutions seem to be more of the same shim type work arounds with no easy / native (within Excel 2011) solution.