HP 3535 - Manual (Page 39)

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2 Sided
Use the 2-Sided feature to select one or two-sided originals, with
options for one or two-sided output.
The following options are available:
1 to 1 Sided Makes one-sided copies from one-sided input. This is the default
setting.
1 to 2 Sided Makes two-sided copies from one-sided input.
2 to 2 Sided Makes two-sided copies from two-sided input.
2 to 1 Sided Makes one-sided copies from two-sided input.