My HP Officejet pro K550 is only printing the first few lines of my document, then it just stops, does not even return the paper???

This is normal for this model of HP printer when the ink has 'expired'.
Normally it will print one line from the print head, then check to see if the ink is okay before pumping more ink into the printhead. If it has expired then it pauses in the middle of printing to give the user an opportunity to replace the ink cartridge with a new one, highlight which cartridge needs replacing by lighting and indicator over the 'bad' cartridge.

There are three solutions for this:

1. Buy a new HP Ink cartridge;
   expensive and innefficient, but it will ensure the highest level of quality and continued warranty for your HP printer. And is the least likely to cause problems.
   
   
2. Buy a third-party "refillable" ink cartridge, or MOD chip;
   Less expensive, but still wastes what remaining ink you have in that ink cartridge. Voids the warranty for your HP printer and can lead to a print head clog.
   
   
3. Set your system clock and print like it's 1999;
   Silly printer driver reads the system time to determine if it has expired; will cause the printer log to be inaccurate, and cause problems with software updates, security certificates and other time-sensitive applications. May requirie shutting down both PC and printer simultaneously to be effective.
   
   
4. Crack/Patch or replace the printer driver to remove expiry;
   3rd party replacement drivers are unable to match the resolution of HP's original drivers because they don't know HP's secret PCL codes. Cracking/Patching HP drivers may be illegal depending on where you live and what security clearance you have. It may also possibly sometimes break features like document control and printer logging.
   
   
5. Buy another printer
   Expensive and wasteful.