In JavaScript this is given by the value of the pageNum document property, so you could get it that way.
http://livedocs.adobe.com/acrobat_sdk/9.1/Acrobat9_1_HTMLHelp/JS_API_A croJS.88.414.html
..... perhabs in connection with this;
http://forums.adobe.com/message/4587057#4587057
However, full Adobe Acrobat is needed for both (not Reader only).
HTH, Reinhard
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