How to Add a Signature Field to a PDF Form (2026)

A signature field is an interactive AcroForm element that recipients click to apply their signature — typed, drawn, or certificate-based. This is different from inserting a signature image onto a page. Signature fields are the right choice when you're sending a form for others to sign, because they make the signing location explicit and support digital certificate signatures.

Signature Field vs Signature Image: Which Do You Need?

Signature field (AcroForm): An interactive element embedded in the PDF. Recipients click it to open a signing dialog, draw or type a signature, and apply it. Supports both simple signature images and PKI-based digital signatures. Best for: forms you're distributing for others to sign.

Signature image: A static image of a signature pasted onto a PDF page. No interactivity — just an image. Best for: applying your own signature to a document you're returning.

This guide covers adding interactive signature fields. For applying a signature image to a document, see how to sign a PDF on mobile or use OnlinePDFEdits.

Method 1: Adobe Acrobat Pro — Prepare Form

Acrobat Pro's Prepare Form tool is the most complete way to add signature fields with full control over appearance and permissions.

Adding a signature field:

1. Open the PDF in Acrobat Pro
2. Go to Tools → Prepare Form
3. Click Start
4. In the Prepare Form toolbar, click the Signature Field tool (looks like a pen with a cursive S)
5. Click and drag on the page to draw the signature field area
6. A field appears with a default name like "Signature1"
7. Double-click the field to open Properties

Signature field properties to set:

• Name: Use a meaningful name ("signer_signature" or "customer_signature") — this appears in the Fields panel and is used when extracting data
• Tooltip: Text that appears when hovering over the field ("Please sign here to authorize")
• Appearance: Set the border color, fill color, and font for the signed name display
• Signed: Choose what happens after signing — "Mark as read-only" locks other fields after signing, useful to prevent form modification after it's signed

Setting up a signature that locks the form on signing:

1. Double-click the signature field → Properties → Signed tab
2. Select "Lock document after signing" or "This script executes when field is signed" for custom behavior
3. This is useful for contracts where the recipient's signature should freeze all fields

Saving with Reader-enabling: By default, Acrobat Reader users can see signature fields but may not be able to save the signed PDF without Reader-enabling. To fix:

1. File → Save As Other → Reader Extended PDF → Enable More Tools
2. Save — now Acrobat Reader users can sign and save

Method 2: LibreOffice Writer (Free)

LibreOffice doesn't have a native "Signature Field" form control in the traditional sense — it has a general form control suite. For a signature-ready field:

1. Open LibreOffice Writer
2. View → Toolbars → Form Controls
3. Click Text Box in the toolbar
4. Draw a box where the signature should go
5. Right-click the box → Control Properties
6. Name it "signature" and add a tooltip "Signature:"
7. Before the field, add a label: "Authorized Signature: _______________"

Export to PDF (File → Export as PDF → check "Create PDF form"). The resulting text box becomes a fillable text field — recipients can type their name, but it's not a dedicated signature field with certificate support.

For a proper digital signature field in LibreOffice's exported PDF, the form needs to be opened in Acrobat Pro after export and a signature field added there. LibreOffice's form controls don't map to the Signature field type in PDF's AcroForm specification.

Method 3: Online PDF Editors

For adding a signature field to an existing PDF without software:

1. Go to OnlinePDFEdits
2. Upload the PDF
3. Use the signature tool to add a signature element
4. Position it on the page where the signature should go
5. Download the updated PDF

This works for most basic use cases. The resulting field allows recipients to draw or type a signature when they open the file.

Method 4: pdftk + Python (Programmatic)

For adding signature fields programmatically — useful when generating PDFs from a template and always needing a signature field in the same place:

import fitz  # pip install pymupdf

def add_signature_field(input_path, output_path, page_num=0, rect=(100, 700, 400, 740)):
    doc = fitz.open(input_path)
    page = doc[page_num]
    
    # Add a signature widget
    sig = page.add_widget(fitz.Widget())
    sig.field_type = fitz.PDF_WIDGET_TYPE_SIGNATURE
    sig.rect = fitz.Rect(*rect)  # (x0, y0, x1, y1) in points
    sig.field_name = "Signature1"
    sig.field_label = "Authorized Signature"
    sig.text_color = (0, 0, 0)
    sig.border_color = (0, 0, 0)
    sig.border_width = 1
    sig.fill_color = (1, 1, 1)  # White fill
    sig.update()
    
    doc.save(output_path)
    doc.close()

add_signature_field("template.pdf", "signable.pdf", page_num=0, rect=(100, 50, 450, 100))

Note: PyMuPDF can add signature field widgets but doesn't apply digital signatures — it creates the interactive field that recipients use to sign with their own certificates.

Multiple Signers: Ordering and Routing

When a document needs signatures from multiple people:

Adding multiple signature fields:

1. Add a separate signature field for each signer (Signature1, Signature2, etc.)
2. Name them clearly: "approver_signature", "customer_signature", "witness_signature"
3. Position them in the intended signing order

Controlling signing order in Acrobat: Each signature field can be set to lock certain other fields when signed — creating a workflow where the first signer's signature must precede the second:

1. Signer 1's field: Properties → Signed → lock all other fields except Signer 2's field
2. Signer 2's field: Properties → Signed → lock all fields

This ensures documents can't be submitted with just one of the required signatures.

For managed multi-signer routing: Use an e-signature platform (DocuSign, Adobe Sign) rather than manual PDF fields. Platforms handle delivery sequencing, reminders, and completion notifications automatically.

Appearance of the Signed Field

After a recipient signs a signature field, the field displays their signature. The default appearance in Acrobat shows:

• The signer's name (from the certificate or typed name)
• The date of signing
• The reason for signing (if set in the signature dialog)
• A certificate icon indicating whether the signature is certified

You can customize the appearance in Properties → Appearance tab. Some organizations use company-branded signature appearance templates.

Testing Your Signature Field

Before distributing the form:

1. Open the PDF in Acrobat Reader (free) — Reader is what most recipients will use
2. Click the signature field
3. Complete the signing dialog — drawn signature, typed name, or certificate
4. Verify the signature appears correctly in the field
5. Save and reopen to confirm the signature persists

Test on multiple platforms if recipients use different operating systems or PDF readers.

FAQ

Can a recipient sign my PDF form without Acrobat?

Yes — signature fields work in Acrobat Reader (free), iOS Markup, Android with Acrobat Reader, and some other PDF apps. For drawn or typed name signatures, most mobile PDF apps handle it. Certificate-based (PKI) signatures require Acrobat Reader or a reader that supports digital certificate signing. Chrome, Edge, and Firefox can display signature fields but often can't sign them.

How do I prevent someone from removing a signature after signing?

Enable "certifying" the document with the signature: in Acrobat Pro's signature dialog, choose "Certify Document" instead of "Sign Document." A certified signature is more restrictive — it defines what changes are permitted afterward. The first certifying signature on a document takes precedence, so whoever signs first effectively locks the allowed modification scope.

What's the difference between a Signature field and a Digital Signature field in Acrobat?

In Acrobat's form tool, both appear as "Digital Signature" — the distinction is how they're signed. A field can be signed with: (a) a typed name or drawn image (electronic signature, no certificate), or (b) a PKI certificate (digital signature). The field type is the same; what differs is whether the signer has a certificate and whether they choose to apply it. Fields signed with certificates show "Certify" or a blue ribbon; fields signed without certificates show a pen icon.

Can I add a signature field to a PDF that's already been signed?

Yes, if the existing signature's permission level allows it. If the existing signature locked the document ("No changes allowed"), you can't add more fields. If it permits "Form fills and signatures," you can add a signature field. Check by trying — Acrobat will tell you if modifications are restricted.