If your design has variable data (multiple guest names), you should supply a single PDF with 50 pages (for 50 names) - one file only.
For variable data one side (50 page file as above) and a static on the reverse, you can either email the back separately, or include it in your file as the first page. You can include this information in the comments section.
You are more than welcome to email your artwork through to us at firstname.lastname@example.org.
Please be sure to reference your order number in the email so that we know which order your artwork belongs to, along with any important information we might need to know (EG: which product each piece of artwork belongs to, if there are more than one items on your order).
We can accept Zip Files that contain multiple files for your print job.