Cannot print Duplex #482

 * Xreader version (xreader --version) 2.8.3
 * Distribution - (Mint 17.2, Arch, Fedora 25, etc...)
Linux Mint 5.4.0-72-generic #80-Ubuntu SMP Mon Apr 12 17:35:00 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

**Issue**
Two page document, specified to print duplex, is printed as two single-sided sheets, but should be one double-sided sheet.


**Steps to reproduce**
Load this document, specify duplex, then print.
[order-document.pdf](https://github.com/linuxmint/xreader/files/6387537/order-document.pdf)


**Expected behaviour**
Should be one double-sided sheet.


**Other information**
HP M377dw printer. Works fine with other programs.