Originally Posted by HarryT
Embedded fonts will dramatically slow down the page rendering speed. That's almost certainly your problem.
You are right, but only partially right. I spent a whole day digging this issue, and finally found a solution.
xpdf/ipdf don't have a problem rendering embeded fonts, but dealing pdf files with big number of embeded font sets. The file I provided above embeds many sets (90+) of Chinese Type1 font, though each is small in size. xpdf/ipdf are really slow at handling this, while Acrobat Reader and even GS/GV can do the job much better.
This becomes apparent to me when I notice some pdf files created by others that also embed Chinese fonts but xpdf/ipdf won't choke on them. The difference is that they embed Truetype fonts, which unlike Type1 with only 265 max glyphs, may contain thousands in one set. Thus it suffices to embed only 1 or 2 sets of bigger Truetype font in the pdf, v.s., the 90+ smaller Type1 font sets.
The solution to my problem is to create pdf using latex + dvipdfmx, which is able to embed Truetype without rasterizing them (just lilke Type1) in to the final PDFs. I'm attaching the result here. The file size is also smaller than the previous one but not by much, and the speed is blazing fast.
Of course the ultimate solution is to fix xpdf/ipf, but for the moment this little PDF creation trick plays well. I'll document this process in thorough detail on the Content forum, just to help other CJK users.