I think know how this is done, I use it to hack my cartridge life all the time. Slightly off topic but bear with it... When the HP driver software compiles the

I think know how this is done, I use it to hack my cartridge life all the time. Slightly off topic but bear with it... When the HP driver software compiles the file code to send to the printer it also encodes other information. I discovered this because I found out it that the system date of the pc gets encoded along with the print data. More shockingly, prior to encoding the file, the printer checks the "best before date" of each cartridge and compares it to the system date. If your cartridge is beyond the date HP would like you to use it by, it introduces artifacts into the print and the issues a "beware you printer could malfunction with out of date cartridges" message. Simple work around, change your system date to some time in the past before your cartridge expiry date, and hey presto your HP printer starts to work again. Change it back to the present and all of a sudden the artifacts and message appear. If HP can mess with your PDF pre-print, then so can someone else. Personally, I love my HP printer. I just hate what HP do to try to force you to buy more ink. Whenever have non-perishable goods required a "use by" date?