Half of a document in pdfLaTeX, half in XeLaTeX

As far as I know, I cannot use microtype in XeLaTeX, and cannot use fontspec in pdfLaTeX. I am rendering Chinese symbols only on one page, and I need this line: \newfontfamily{\J}[Scale=0.85]{Osaka} to render the symbols properly.

I want to use microtype and fontspec at the same time; is it possible to tell latex to switch into "pdfLaTeX" mode to render the first half of the document, and then switch back into XeLaTeX to render the other half?

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Have you tried LuaLaTeX? fontspec and parts of microtype work with it. –  doncherry Dec 21 '12 at 17:51
I haven't tried LuaLaTeX. I'll give it a shot now. Is there a fundamental syntax change between pdflatex and LuaLaTeX? –  alexy13 Dec 21 '12 at 18:03
Or use pdfpages to insert the second half (pre-generated with xelatex) into the main document generated with pdflatex. –  JLDiaz Dec 21 '12 at 18:19
@alexy13 See my answer. Basically: No, the syntax is the same; the packages typically loaded are a mixture of pdfLaTeX and XeLaTeX packages. –  doncherry Dec 21 '12 at 19:10
If the Chinese part is restricted to one page it would probably be best to compile it with XeTeX and include it using pdfpages. –  Alan Munn Dec 21 '12 at 20:04

I recommend LuaLaTeX, since it supports fontspec and parts of microtype: protrusion and expansion; whereas kerning, spacing, and tracking are not (yet?) supported, cf. the microtype documentation.

For a little background on LuaLaTeX, see:

On your actual question: If you need to switch compilers mid-page, I’m not sure there’s any option other than manually puzzling the pieces together, e.g. with pdfpages, as JLDiaz suggested. Also note that there is a beta version of microtype that supports XeLaTeX, but I don’t know which features; see e.g. neic.dk - XeLaTeX with microtype on TeX-Live 2012.

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Yes, I have experiment with LuaLaTeX and recommend too. It is relative simple to port pdfLaTeX (if you code your doc in UTF-8) and XeLaTeX to LuaTeX. –  lazyboy Dec 21 '12 at 19:48
This is one of the cases where LuaTeX and XeTeX are not equivalent. The standard package for dealing with Asian languages xecjk makes extensive use of XeTeX-specific functionality, especially xetexinterchartoks, which doesn't exist in LuaTeX. See Is there a LuaTeX analogue to xetexinterchartoks. –  Alan Munn Dec 21 '12 at 20:03
@AlanMunn: Thanks, good to know! I've only ever used Latin (and a wee bit of Greek) script with either compiler. –  doncherry Dec 21 '12 at 20:17