Follow the steps below to merge two OneNote notebooks without losing any data.

1. Back upNotebooks:
   Before merging two OneNote notebooks, you must first backup each for safety.
2. Merge Notebooks:
   Launch OneNote and navigate to the 'Notebook' view. Right-click the first notebook and select 'Merge'. Select the second notebook and click 'Merge'.
3. Choose the Destination Notebook:
   Select the destination notebook, which will store the content from both notebooks. Decide which notebook 'wins' any conflicts and complete the merge action.
4. Rename Pages and Sections:
   After the merge action is complete, rename pages and sections if necessary. This will help ensure that no information is lost.
5. Move Pages to Section:
   You can manually move sections from one notebook to another, if desired. This is helpful for organizing notes.