Google Docs supports to upload and preview PDF, It can save PDF page as image, and I notice the default name is gview, and format is png, so I think it seems to base on GSView.

GSview is a graphical interface for Ghostscript.Ghostscript is an interpreter for the PostScript page description language used by laser printers.For documents following the Adobe PostScript Document Structuring Conventions, GSview allows selected pages to be viewed or printed.GSview requires
Ghostscript.GSview is available for Windows, OS/2 and Linux.

From PC Pro, I got Google introduces Presentation PDF support,

Google has added PDF support to the presentations component of Google Docs.
Presentation can now export slides in the PDF format, enabling presentations to be saved offline. There’s also a set of PDF-based printing options that enable up to 12 slides to be printed on single sheet.

So I did a try, it also supports Chinese, but I found it try to use Japanese font by default, so some Chinese characters will be lost, maybe they do not exist in Kanji(Japanese character) database.