Sorry for the multiple posts on this. You sent me on a bit of an adventure:
* Downloaded a modified DOSBox build with printer support from http://ykhwong.x-y.net/ (linked from DOSBox wiki so not too worried)
* Mapped LPT1 in DOSBox to LPT1 in Windows
* installed CUPS-PDF [1] on a CUPS server in a VM
* shared virtual PDF printer via Samba to Windows
* ran net use lpt1: \\vm.local\pdf /persistent:yes
* printed from DOSBox and got [2]
1: http://www.cups-pdf.de/ (or apt-get install cups-pdf)
2: https://mega.co.nz/#!ehpxha4b!U2q9lhH2RoniPKucW862Y2qRxCgMJ6...