How to Sign a PDF Document: A Complete Guide for 2025

In the digital-first world of 2025, signing a PDF document is no longer a task reserved for lawyers or corporate executives. Whether you are a startup founder closing a funding round, or an HR manager onboarding new employees, knowing how to sign a PDF document can save time and ensure legal validity. This guide walks you through different ways to sign a PDF, whether you're using a laptop, mobile device, or cloud platform.

1. Using Adobe Acrobat Reader (Free Desktop Method)

Adobe Acrobat Reader DC is a widely-used and free PDF viewer that also lets you sign documents easily.

• Steps:

  1. Open the PDF file in Adobe Acrobat Reader.

  2. Click on "Fill & Sign" in the right-side toolbar.

  3. Choose "Sign" and then "Add Signature."

  4. You can type, draw, or upload an image of your signature.

  5. Click and drag the signature into place.

  6. Save the document.

• Platform: Windows, macOS

• Cost: Free

2. Using Preview on Mac (macOS Native App)

Mac users can sign PDFs without downloading any third-party apps.

• Steps:

  1. Open the PDF with Preview.

  2. Click the Markup icon (pen tip).

  3. Click the Sign icon, then choose "Create Signature."

  4. Use your trackpad or camera to create a signature.

  5. Insert the signature and save.

• Platform: macOS

• Cost: Free

3. Using Online Tools (No Installation Required)

Several online platforms allow you to sign PDFs quickly without downloading software.

• Popular Platforms:

  • Smallpdf

  • HelloSign (now Dropbox Sign)

  • DocuSign

  • PDFfiller

  • Plox (for secure document sharing + signing)

  Steps (Generic):

  1. Upload your PDF to the platform.

  2. Drag and drop a signature field.

  3. Create or upload your signature.

  4. Apply the signature and download the file.

• Benefits: Cross-device, secure, fast

• Caution: Always use reputable sites to protect sensitive data

4. Using Plox for Document Sharing and Signing

Plox (plox.in) is a powerful platform designed for startups to share and track documents securely. As part of its toolkit, it also lets users add legally valid signatures.

• Best For: Fundraising documents, NDAs, employment contracts

• Key Features:

  • Secure, branded links

  • Signature request workflows

  • Real-time tracking (who opened, when, how long)

  • Audit trail and version control

• Pricing: Free plan available; Paid plans from $29/month

5. Using Mobile Apps (iOS & Android)

Mobile apps make it easy to sign PDFs on the go.

• Recommended Apps:

  • Adobe Fill & Sign

  • SignNow

  • PandaDoc

  Steps:

  1. Open the PDF in the app.

  2. Tap on the signature option.

  3. Draw or upload your signature.

  4. Place it where needed and save or share the document.

6. Signing PDFs in Google Docs (Workaround)

While Google Docs doesn’t directly support e-signatures, you can use a workaround with Drawing tools or add-ons.

Steps:

1. Open the PDF via Google Docs (auto-converts to editable format).

2. Go to Insert > Drawing > + New.

3. Use the scribble tool to draw your signature.

4. Place the signature and download the file as a PDF.

Final Thoughts

Gone are the days of printing, signing, and scanning. Whether you prefer desktop apps, mobile tools, or cloud-based workflows, there's a PDF signing method for every use case. For businesses and startups, platforms like Plox combine signature functionality with analytics and secure sharing, making them ideal for contracts, fundraising decks, or employee onboarding.

Choose the method that best fits your workflow, and stay compliant while saving time.