HP Deskjet 5850 Color Inkjet Printer - Manual (Page 211)

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Flip Pages Up is selected for binding along the top (tablet binding).
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Flip Pages Up is not selected for binding along the side (book binding).
For more information, see two-sided printing .
paper size changes when the two-sided printing option is selected
The paper size is not supported by the duplexer.
See the documentation that came with the duplexer for a list of supported paper
sizes.