Hi, can I link JIRA issues in Confluence? If yes, how and will they be up to date once a JIRA issue changes?
Yes, that is definitely one of the great integration features between both programs! Once you link a JIRA issue in Confluence, it will automatically be updated, as soon as you apply any change in the issue in JIRA.
The easiest and fastest way is to copy&paste. Here you can read about it in an Atlassian blogpost that explains it realy quick: http://blogs.atlassian.com/2013/07/display-jira-issues-in-confluence-more-power-more-control/
Here you will find some extra tips: http://blogs.atlassian.com/2012/02/link-jira-issues-to-confluence-pages-automatically/
And how to link a Confluence page with JIRA on the other hand: https://confluence.atlassian.com/agile/jira-agile-user-s-guide/working-with-epics/linking-a-confluence-page-to-an-epic