Check The "Allow Edit" Checkbox
If you find yourself in need of editing a document after it’s been generated, no worries! The S-Docs Live Edit feature enables end-users to open and edit generated documents wherever they're linked in Salesforce.
To enable this feature, navigate to the template record detail page for the template that should be editable after generation. Click the dropdown arrow on the right, and then click Template Editor to open up the S-Docs template editor.
Navigate to the Document Options tab, then check the Allow Edit checkbox, which can be found under the Attachment & File Options section.
After you save your template, an edit link (a pencil icon) will appear next to the document each time it is generated.
In this example, we’re going to generate an invoice from an Opportunity. The process is the same as any other document generation. We’re going to select the “Standard Invoice” document and then click Next Step.
Once your document is generated, you can edit it by clicking the pencil icon. You can also click Emailed Selected Docs to proceed to the email page and make your edits from there, or find the document in the S-Docs related list on the record that you generated the document from. The pencil icon will appear wherever this document is stored in Salesforce, allowing you maximum editing flexibility. We'll click the pencil icon now.
The live edit screen will appear as follows in a new tab:
You can  make edits to your document and use the toolbar to apply styling.  Click Save to save your changes, and then  click Preview Last Save to preview how your changes will appear in the final document.
If you're not happy with your edits,  click Revert Last Save to undo your changes.  Click Close to close the edit window and return to the page you started from (in this case, the generated documents page).
That's all there is to it!
By default, all users with S-Docs licenses enabled are able to edit documents that have the live edit feature enabled. However, you can also disable live editing for all users by default and allow only specific profiles to use the feature.
To do so, navigate to the S-Docs Setup tab by clicking the App Launcher, typing in "S-Docs," and clicking S-Docs Setup in the dropdown menu.
Scroll down to the Other Settings section. From there, you can  enter a new-line delimited list of profile names that should have access to live editing. Then,  click Update Settings. Only users with profiles in the list will be able to live edit documents.
While the Live Edit feature is convenient way to modify documents after they have been generated, it does come with a few limitations.
- PDF, PDF-Upload, and HTML are the only file output types supported.
- Editing cannot be restricted to certain sections of the document; the Live Edit feature gives users access to edit the entire document (except for PDF-Upload templates. With this format, only merged field data can be edited).