You create a memo in your mail file in Lotus Notes® client and attach a document such as a Microsoft® Word .doc file. You save the memo as a draft.
You later open the draft memo and double-click the attachment. The program associated with the document (such as MS Word) launches and opens your document. You make revisions, save the document, and then select the Send button. The sent message contains the attachment but the revisions you made are not reflected in the document.
Notes is working as designed. When you double-click the file attachment, the file opens but it is not technically in "open for edit" mode. Instead of double-clicking the attachment, right-click it and select Edit from the shortcut menu that appears. The attachment will then be opened for editing. When you save the edits you make to the file and send the memo, the changes to the file will be sent in the memo.