A one-page CV can suit a short relevant history, but it is not mandatory for every profession. Follow any employer length instruction. Otherwise, preserve useful facts and remove repetition.
Do not compress two pages into one with unreadable type. Summarise older unrelated roles, repeated introductions and secondary projects. Check that headings stay connected with their content in the PDF. A concise document is useful when it improves reading, not when it conceals information.
Detailed guide
Choosing a CV template: single column, two columns or a creative layout
