On macOS, Preview lets you add a signature to PDF and image documents using your built-in camera, iPhone, iPad, or an existing saved file. The preferred, persistent location for these signatures is the Keychain-backed Signature Vault managed by Preview, though you can also store signed copies in any user directory. This evergreen explainer details how to import a signature into Preview on any modern macOS release, compares storage locations, and outlines verification and management steps to keep your signing workflow secure and reliable.
What It Means to Import a Signature into Preview
Importing a signature into Preview means adding a reusable signature asset that the app can reference when you sign documents electronically. Unlike a one-off pasted image, an imported signature becomes a managed item that Preview can cryptographically bind to signed content, leveraging the macOS security model. This process normally creates or references an entry in Preview’s Signature Vault (secured by your user login keychain) and associates it with your Preview identity. When you later sign a PDF or image, Preview uses this signature material while recording signing metadata in the document’s signature dictionary.
Where macOS Stores Signature Assets
Preview stores imported signatures in its per-user signature vault, which is backed by the macOS keychain system and tied to your user account and login keychain. This vault is not a plain file you can freely copy, but Preview can export signed copies and signature images to any folder you choose. For audits and portability, you can export a signature as a reusable image or PDF stamp; for identity and integrity, rely on the vault entry and associated certificate rather than file copies alone.
Signature Storage Options and Tradeoffs
| Storage Location | Persistence | Security and Access | Use Case |
|---|---|---|---|
| Preview Signature Vault (keychain-backed) | Persists across reboots; per user | Bound to login keychain; requires account password | Primary signing identity for Preview |
| Exported image file (e.g., PNG, JPEG) | Persists until manually deleted | File system permissions only; no keychain binding | Sharing or archival copies |
| Exported signed PDF or stamp | Persists until manually deleted | Document-level signature remains verifiable | Delivering completed, signed documents |
How to Import a Signature into Preview (Step-by-Step)
The most common workflows are using the camera to capture a signature on an iPhone or iPad, or importing an existing handwritten signature image from your Mac. Preview then registers the signature in its vault so it remains available across documents without re-capturing each time.
Capture a Signature with an iOS Device
- On your Mac, open a PDF in Preview and choose Markup Toolbar > Signature > + Add Signature.
- Select Use iPhone/iPad, which displays a QR code on the Mac and opens the Camera on your iOS device.
- Sign the paper with your finger or stylus, then tap Done; the signed image appears on the iOS device and uploads to Preview’s vault on the Mac.
- Preview confirms the signature as available for future signing tasks.
Import an Existing Signature Image
- In Preview on Mac, choose Markup Toolbar > Signature > + Add Signature.
- Select Import from File and locate a handwritten scan or clear photo of your signature.
- Preview attempts to isolate the signature and places it on a clean white background.
- Adjust the cropping box so only the signature remains, then click Done to store it in your vault.
Verify the Imported Signature
Once imported, Preview lists the signature under Markup Toolbar > Signature. When you select it for signing, a small info badge may appear showing the associated identity or certificate, if any. You can delete signatures you no longer need from the same Signature menu; removal deletes the item only from Preview’s vault and does not affect other keychain items.
Best Practices for Managing Signatures
Because signatures are tied to legal intent and document integrity, treat them with the same care as other identity credentials. Store your login keychain securely, enable FileVault if the device is portable, and avoid exporting raw signature images to untrusted locations. If you frequently sign for others, consider creating separate identities rather than reusing a single signature. Periodically review the list of stored signatures and remove any that are outdated or unnecessary.
Troubleshooting Signature Import Issues
If Preview cannot import or recognize a signature, first confirm that the image has high contrast and a plain background. Photos with shadows or grid lines can confuse detection; manually crop to the signature region to improve results. If the signature appears in the vault but cannot be used for signing, check that Preview has permission to access the keychain and that your user account password is correct; keychain issues often block signature lookup without displaying obvious errors.
Signature Lifecycle and Recovery
Your imported signature remains available until you explicitly delete it, change your keychain password, or erase the Mac. If you reassign your login keychain or migrate to a new Mac, export any non-obvious identities and reimport them so they remain usable. For compliance-sensitive workflows, export signed copies with embedded validation information; this does not replicate the vault entry, but it preserves the visible signature and certificate details for later verification.