Hello,
The corresponding fields in the REST API are
width and
height. Here is a cURL example:
$ curl -F "username=***" -F "key=***" \
> -F width=8.5in \
> -F height=11.in \
> -F 'src=http://www.google.com' \
> http://pdfcrowd.com/api/pdf/convert/uri/ > google_com.pdf