I've seen a project that your Voltera colleague made. It uses a 2x3 substrate, and prints a name at the top, a logo and company name at the bottom, then some additional info (telephone and email) at the bottom right. A rectangle serves to frame the card and ink printing the rectangle is broken to allow one resistor and two LEDs to complete a 9V powered circuit. I tried uploading an image which didn't work, sorry.
The questions I have are:
1) What arrangement of how many 1206 LEDs in serial will work, 2 or 3?
2) How can I buy a reel of these LEDs and be sure they are the right kind?
3) Are they the same LEDs as in the hello world kit?
4) How many ohms resistance is required?
I'm a little puzzled by why 9V across 2 LEDs is not burning them out.