You can find many ways to specify the VLANin your network configuration but Ifind this is the simplest and quickest.
In this case we are talking about a bridged adapter "vmbr0" but it works even if you just had a normal non-bridged interface.
The key here is that in vmbr0 you'll notice there is no IP address. We just specify "manual".
Below it is a similar stanza for "vmbr0.58" in this case 58 represents the VLAN (change........
convert -density 200 file.pdf file.jpg
Increase the "density" value to get a higher resolution/larger file an decrease it to go smaller.
This is really the quickest and simplest way.
Some issues you may have: