Hello,
The current version of the PDF plugin just have to supported tags :
The first one is to include the serial data and the second one to insert a unique ID.
But we can improve the plugin to add more tags and support for example the Order ID or the Order Number.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.