I have found the issue. It was a known issue of civicrm v5.25. Here is the details: https://github.com/civicrm/civicrm-core/pull/17164/files
"Invoices - print and email" has been appeared in the dropdown menu after implementing the patch. Thanks everyone for the help
To this very old but unanswered question, I'll answer that there's now an extension that does exactly what you're asking: Clone Contribution. Quoting from the description:
This extension provides:
UI controls to clone a particular contribution, wherever contributions are listed (e.g., a contact's Contributions tab;
contributions search ...
It will depend on how the contributions were created and whether payments were associated with it.
The best ERD I know of is this one doc.symbiotic.coop/dev/civicrm/latest/schema/index.html
At a minimum you will probably need to check the civicrm_line_item table as well as civicrm_contribution.
Go to Contributions menu » Find Contributions (or use Advanced Search with Display Results as set to Contributions.
Search for the invoices you want to send by setting Contribution Status to Pending and any other criteria you need.
Select "all X records" or manually select the invoices you want to send from the result.
From the Actions menu, select ...