enc = doc:GetEncoder(encodingname)
doc:GetEncoder() gets the handle of an encoder object by specified encoding name.
See Encodings for a list of valid encoding names.
When doc:GetEncoder() succeeds, it returns the handle of an encoder object. Otherwise, it returns Nil and the error handler is called.
#HPDF_INVALID_DOCUMENT - An invalid document handle was set.
#HPDF_FAILED_TO_ALLOC_MEM - Memory allocation failed.
#HPDF_INVALID_ENCODING_NAME - An invalid encoding name was set.