On a Chromebook, Gmail runs in Chrome, so the same tools work as on Windows or Mac. Chromebooks often have little storage, which is one more reason to prefer preview over saving copies you do not need.
1. Use Gmail's preview (received mail)
Open the email and click the attachment card (not the download arrow). Gmail shows PDFs, images (including HEIC), text and many Office files in its own full-screen preview. Nothing goes to Downloads. Press Esc to close.
2. Make sure Chrome opens PDFs instead of saving them
Go to chrome://settings/content/pdfDocuments and choose Open PDFs in Chrome.
3. Preview inside Gmail, including in compose
In compose, reply or forward, clicking an attachment chip downloads the file. To check a PDF or image before sending without downloading, use Attachment Preview. Attachment Preview is a free Chrome extension, and Chrome extensions install on Chromebooks the same way as on any computer.
- Open the Chrome Web Store link and click Add to Chrome.
- Open Gmail. Under PDF and image attachments you will see a Preview button; other files get Open in new tab.
- Click Preview. The file opens on top of Gmail (overlay, page counter). Press Esc to go back.
Nothing is saved to your Chromebook's Downloads folder from Preview, and nothing is sent anywhere.
School or work Chromebook? Your administrator may block extension installs. If Add to Chrome is greyed out, ask them to allow the extension, or use options 1 and 2 for received mail.
Free up space from old downloads
Open the Files app, go to Downloads, sort by date, and delete attachment copies you no longer need.
Related: Open a PDF in Gmail without downloading · Gmail attachments not opening