Yes — Send Proposal can be used as many times as you like. Each send emails the selected customers again (with fresh PDF/BEO attachments if enabled) and logs nothing beyond the first Proposal sent entry; the status only changes from New to Sent the first time and is otherwise left as it is. If the customer had already accepted and you changed pricing, consider clearing the contract signature (which reverts the proposal to Sent) so they review and sign the updated version.