The system is protected by firewall and VPN. Then I printed it in the printer connected in the network.
If you're talking about VPN which owned by place where you work, they could
1. Record your traffic.
2. Setup proxy on VPN system which used to intercept/decrypt HTTPS connection.
3. Perform DNS spoofing to redirect you to fake website.
The network is very safe - I will not tell the name of company for privacy.
What makes you think the network is very safe? Are you the one who manage/secure the network on that company?