How to Compare Two PDF Files Side by Side

Need to spot the differences between two PDF documents? Whether you are reviewing contracts, checking revisions, or verifying that nothing important changed, comparing PDFs side by side saves hours of manual checking. Here are the best free methods to do it.

Why Compare PDF Files?

PDF is a final format. Once a document is exported to PDF, tracking changes becomes much harder. Common scenarios where comparison is essential:

• Legal contracts — make sure no clauses were secretly modified between versions
• Academic papers — verify edits from reviewer feedback
• Invoices and reports — catch discrepancies in numbers or details
• Design proofs — confirm layout changes match expectations

Method 1: Online PDF Comparison Tools (Quickest)

The fastest way to compare two PDFs without installing anything:

Diffchecker

Upload both PDFs to diffchecker.com. It extracts text from both files and highlights additions, deletions, and modifications. Free for basic use with a generous file size limit.

Adobe Acrobat Online Compare

Adobe offers a free online comparison tool at acrobat.adobe.com. Upload your two PDFs and it generates a detailed report showing all text and formatting differences with color-coded highlights. The output is professional and easy to read.

Draftable

Draftable provides a clean side-by-side view with scroll syncing. It highlights differences in both text and visual elements. The free version handles files up to 50MB each.

Method 2: Desktop Software for PDF Comparison

Adobe Acrobat Pro

The gold standard. Go to Tools > Compare Files, select your two PDFs, and Acrobat generates a detailed comparison report. It shows text changes, image differences, and even formatting variations. Requires a subscription, but you can use the 7-day free trial.

Beyond Compare (with PDF plugin)

A powerful file comparison tool for Windows and Mac. With the PDF plugin, it can compare PDF content directly. It excels at three-way comparisons and folder-level diffing. Not free, but reasonably priced for professionals.

Method 3: Manual Side-by-Side Comparison

For visual comparisons where automated tools fall short:

1. Open both PDFs in your browser or PDF reader of choice.
2. On Windows: snap one window to the left half of your screen and the other to the right using the snap feature (Win + left/right arrow).
3. On Mac: use Split View by hovering over the green fullscreen button.
4. Scroll through both documents at the same pace.
5. Take screenshots of any pages with differences for your records.

Method 4: Convert to Text and Use a Diff Tool

If you only care about text differences and the PDFs contain mostly text:

1. Copy all text from both PDFs (Ctrl+A then Ctrl+C in a PDF reader).
2. Paste each into separate text files.
3. Use a free diff tool like diffchecker.com or VS Code's built-in comparison feature.
4. The diff output shows every text change between the two versions.

Method 5: Command Line (For Developers)

If you are comfortable with the terminal:

• diff-pdf — open source tool that visually compares PDFs and can output a PDF with differences highlighted
• pdftotext + diff — convert PDFs to text using Poppler's pdftotext, then use the standard Unix diff command
• Python with PyPDF2 — write a script to extract and compare text content programmatically

Which Method Should You Choose?

• Quick one-time comparison — use an online tool like Draftable or Diffchecker
• Professional document review — Adobe Acrobat Pro Compare Files
• Visual or design-focused comparison — manual side-by-side view
• Bulk or automated comparison — command line tools or scripts
• Budget conscious — convert to text and use free diff tools

Tips for Better PDF Comparisons

• Always compare the latest versions — double-check file dates before uploading
• Use the older document as the base and the newer one as the changed version
• Pay attention to headers, footers, and page numbers — these often change between versions
• After comparing, save the comparison report as a separate PDF for your records

Frequently Asked Questions

Can I compare scanned PDFs?

Automated comparison requires text content. If your PDFs are scanned images, run OCR first using a free tool like Google Drive OCR or Adobe Scan, then compare the extracted text.

Is there a free way to compare PDFs with images?

Draftable's free tier handles visual comparisons including images. For more detailed image diff, open both PDFs and take screenshots of each page, then overlay them in an image editor at 50% opacity.

How accurate are online PDF comparison tools?

Most tools are highly accurate for text changes. Visual and formatting differences are harder to detect automatically. Adobe Acrobat Pro is the most reliable for comprehensive comparison including images, fonts, and layout changes.