How can I reset my alarm system?

Hia, I have a Eurotec PR5208 (Rev 1.0) alarm system installed ( already in the house when I moved in ) and I lost the code to it about a year ago.
Do I need to reset the system in order to use a code I can remember and how would I do this ? There was no manual in the house when I moved in just a piece of paper with the alarm code on.