Someone emailed a PDF that needs a quick fix — sign here, change this number, fill that field. Gmail shows the preview but doesn't edit. Most people end up downloading, opening in a desktop app, editing, attaching to a reply.
Four steps becomes two when both tools live in the browser.
Two-tab Gmail flow
Open the email. Click the PDF preview to expand. Click the download icon. The file lands in Downloads.
Open Flint in a new tab. Drag in the downloaded file (from Downloads or even from Chrome's download bar directly into the Flint tab). Edit, sign, or whatever. Download the result.
Back to Gmail. Hit Reply. Attach the edited file. Send.
Save to Drive as middle step
Gmail has a 'Save to Drive' button on attachments. Useful if you want to preserve the original in Drive and edit a separate copy. Click it, open Drive, download from Drive, edit in Flint, upload edited version to Drive, attach Drive link to email reply.
More steps but cleaner for long-running document conversations.
Bigger attachments
If the edited PDF approaches Gmail's 25 MB limit, compress in Flint first. Saves the recipient bandwidth and avoids Gmail offering to convert to a Drive link automatically. For very large files, just use Drive link directly.
FAQ
Can I edit attachments inline in Gmail?
No — Gmail's preview is read-only. The download-edit-attach flow is the standard. Some browser extensions add inline editing but most route through web apps anyway.
Will my reply with the edit go to the right people?
Reply or Reply All as usual. The edited file attaches like any new attachment. Recipients see the attachment in your reply; they don't see the original separately unless they look at the thread.
Should I mention the file is edited?
Polite practice — say what changed in the email body. 'Updated the date and signed' or similar. Recipients know what to look for.
Two tabs. Edit in Flint, reply in Gmail, send.