Reader 9 app.execMenuItem ("SaveAs") throw: The document could not be...

I have a compatibility problem with Reader 9.

I have designed a PDF with Adobe LiveCycle Designer ES 8.1. and a button, the JS code:

app.execMenuItem("SaveAs");

But if I use Reader 9, get the error message:

"The document could not be saved. There was a problem reading this document (105)."  (if I use Reader 7 or 8 version works).

Why? How do I solve this?

Thank you!