This is the same as a bug in the early days of the Chrome PDF viewer, and I believe it was once a bug in eBookDroid which was probably inherited here.
I think that bug is mentioned here:
http://code.google.com/p/ebookdroid/issues/detail?id=498&q=font&colspec=ID%20Reporter%20Opened%20Type%20Status%20Priority%20Milestone%20Owner%20Summary
It looks like it was fixed just after they closed the source. I can confirm that the same book mentioned there, at http://press.princeton.edu/chapters/s6946.pdf, does not render properly on PDFViewer.
This is the same as a bug in the early days of the Chrome PDF viewer, and I believe it was once a bug in eBookDroid which was probably inherited here.
I think that bug is mentioned here:
http://code.google.com/p/ebookdroid/issues/detail?id=498&q=font&colspec=ID%20Reporter%20Opened%20Type%20Status%20Priority%20Milestone%20Owner%20Summary
It looks like it was fixed just after they closed the source. I can confirm that the same book mentioned there, at http://press.princeton.edu/chapters/s6946.pdf, does not render properly on PDFViewer.