For a document, if you have two records which are identical, and meant for common purpose, you can merge them into one record.
Following are step to merge documents. Let's assume we are merging two Accounts.
Step 1: Go to Chart of Account
Accounts > Documents > Chart of Accounts
Step 2: Go to Account
For an Account to be merged, click on the "Rename" option.
Step 3: Merge Account
In the New Name field, enter another account name with which this account will be merged. Check "Merge with existing" option. Then press 'Rename' button to merge.
Following is how the merged account will appear in the Chart of Accounts master.
Effect of Merging
After Account is merged, new name is updated in the existing transactions where old account was selected.