Cách ký tệp PDF trực tuyến miễn phí — Hướng dẫn từng bước

There are two types of signatures commonly used with PDF documents:

**Electronic signature (eSignature):** An image of your signature — drawn with a mouse, typed, or uploaded as a PNG — placed on top of the document. This is what WhiskFile's Fill and Sign PDF tool creates. It is legally valid in most jurisdictions for most document types.

**Digital signature (cryptographic):** A mathematical certificate embedded in the PDF that cryptographically proves who signed it and that the content has not changed since signing. Required for high-stakes contracts, regulated industries, and jurisdictions that require qualified electronic signatures (QES) under eIDAS. WhiskFile creates electronic signatures, not cryptographic digital signatures.

1. Go to the WhiskFile Fill and Sign PDF tool.

2. Upload your PDF. The document will open in the signing editor.

3. Choose your signature type: - **Draw:** Use your mouse or touchscreen to draw your handwritten signature - **Type:** Type your name and choose a handwriting-style font - **Upload:** Upload a PNG image of your physical signature

4. Click where you want to place the signature on the document. Resize and reposition as needed.

5. Click "Apply Signature" and then "Download Signed PDF". The signature is permanently embedded in the PDF.

1. Upload your PDF form to the Fill and Sign PDF tool.

2. Click on each form field (text boxes, checkboxes, dropdown menus) to fill in your information.

3. Add your signature as described above.

4. Click "Download" to get the completed, signed form.

Note: This works for interactive PDF forms (fields created by the document author) and for non-interactive PDFs where you add text as overlays.

In most countries, an electronic signature — including a simple image of your handwritten signature placed on a PDF — is legally valid for most personal and business documents. This includes the United States (under the E-SIGN Act and UETA), the European Union (for simple electronic signatures under eIDAS), the UK, Canada, Australia, and most other jurisdictions.

Exceptions: Wills, codicils, and certain court filings may require wet (physical) signatures depending on local law. Always consult a legal professional for high-stakes documents.

After signing, use the WhiskFile Flatten PDF tool to permanently embed the signature into the page content. A flattened PDF cannot be edited without visibly altering the document — the signature cannot be removed without destroying the page.

For additional security, apply password protection using the Protect PDF tool to restrict editing after signing.