There is no "merge documents" feature but you can do it manually. Below are some examples of how to do it but it is not an exhaustive list of all the ways to select, copy, and paste items from one place to another.
If your other documents are just a single table each, you can use Copy/Paste to copy each table from the old document to the new one.
- Select the table (Click on it then click the circle that shows up at the top left corner)
- Copy
- In the new document click on a blank spot on the canvas
- Paste
Or, if each of your Numbers documents consist of a single sheet with multiple tables and/or charts (but all are on one sheet),
- Open the document you want as your new one
- Open one of your old documents
- In your old document, right click on the tab for the sheet and choose Copy Sheet
- In your new document, right click on a sheet tab and choose Paste Sheet
- Repeat 2-4 for other old old documents.
Or, if your old documents have multiple sheets you can do one of two things:
- If the sheets are independent (no formulas or charts referencing cells/ranges on a different sheet), you can use the same Copy/Paste or Copy Sheet/Paste Sheet method as detailed above for each sheet.
- If there are references to other sheets, move everything to one sheet then do the Copy Sheet/Paste Sheet method detailed above. You move table and charts from one sheet to another using Cut then Paste.
