Apple yesterday pushed out a pre-release version of Safari 5.1.2 to Mac developers. The update addresses several issues related to the viewing of PDFs located within frames on websites while also asking developers to test plug-in interaction and printing. From the seed notes:
Inline PDF Support
Safari 5.1.2 fixes issues where PDFs in frames were not displayed in the browser. Please test this build with websites that display PDF documents inline such as banks and document management systems. Please also test saving and using context menus with PDFs in frames.
Please test mouse and keyboard interaction in plug-ins with input fields.
Please test printing web pages. Printing web pages to PDF is sufficient.
Apple documents one known issue which could cause Safari to crash using certain Safari Extensions.
Safari 5.1.2 is available to developers in versions for OS X Lion, Mac OS X Snow Leopard, and Windows.