Scanning Documents to PDF with Adobe Acrobat

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Why Scan to PDF?

Despite the widespread adoption of digital workflows, paper documents remain a reality for most organisations. Contracts are signed on paper, historic records exist only in physical form, correspondence arrives by post, and compliance requirements often demand retention of original paper documents alongside their digital counterparts. Scanning to PDF is the standard way to bridge the paper and digital worlds.

PDF is the preferred format for scanned documents because it is self-contained, widely supported, compact relative to raw image formats like TIFF, and capable of carrying searchable text (via OCR), metadata, bookmarks, and annotations alongside the page images. Adobe Acrobat's built-in scanning interface provides direct control over scanner hardware and the resulting PDF output, making it the most capable end-to-end scanning solution for organisations that rely heavily on PDF workflows.

Scanning Directly from Acrobat

Acrobat communicates with TWAIN-compatible and WIA scanners on Windows, and Image Capture-compatible scanners on macOS. If your scanner is installed and recognised by the operating system, it will be available from within Acrobat.

Starting a Scan

1. Open Acrobat Pro and go to Tools > Scan & OCR.
2. Click Scan a Document.
3. Select your scanner from the scanner dropdown list.
4. Choose a preset from the document preset list, or configure settings manually (detailed in the sections below).
5. Place your document in the scanner and click Scan.
6. After the first page is scanned, Acrobat will ask whether you want to scan more pages or complete the document. Continue scanning pages as needed, then click Done to finalise the PDF.

Scanner Settings: Resolution

Resolution — measured in dots per inch (dpi) — determines how much detail is captured from the original document. Choosing the right resolution involves a trade-off between quality and file size.

• 150 dpi: Adequate for on-screen viewing only. Text will appear legible on screen but printing quality will be poor. Produces very small files. Not recommended for archiving or OCR.
• 300 dpi: The standard setting for most document scanning. Provides good quality for both on-screen use and printing, and produces reliable OCR results for normal body text. This is the recommended minimum for any archival or searchable-text workflow.
• 600 dpi: Recommended for documents with small print (below 8pt), fine lines, technical drawings, or any content that requires high fidelity. Produces significantly larger files — expect a 300 dpi black-and-white file to be roughly one quarter the size of the equivalent 600 dpi scan.

Scanner Settings: Colour Mode

The colour mode affects both file size and OCR performance.

• Black and white (bitonal): Each pixel is either black or white. Produces the smallest files. Best for typed text documents, simple forms, and anything without greyscale or colour content. At 300 dpi, bitonal scans give excellent OCR results.
• Greyscale: Each pixel captures a shade of grey. Slightly larger files than bitonal, but better at preserving images, photographs, diagrams, and text with subtle contrast variations. A good choice for documents with mixed content — text plus images.
• Colour (24-bit): Full colour capture. Required for documents where colour is meaningful — branded stationery, coloured forms, marketing materials, photographs. Produces the largest files. Use JPEG compression within the PDF to manage file size.

Duplex Scanning

If your scanner supports duplex (double-sided) scanning, Acrobat can capture both sides of each page in a single pass. Enable this in the scanner settings dialog — look for Both Sides or Duplex in the side selection option. Acrobat will automatically assemble the front and back pages in the correct sequence in the output PDF. Confirm that your scanner's duplex feed is correctly configured before scanning important documents, as some scanners require specific feed orientation settings to produce the right page order.

Auto Document Detection and Deskewing

Acrobat includes automatic image enhancement features that are applied after the raw scan data is received:

• Auto-detect colour: Acrobat analyses each page and automatically switches between colour/greyscale and black-and-white compression based on the content, helping to keep file size down for documents with mixed page types.
• Deskew: Automatically detects and corrects pages that were placed at a slight angle in the scanner. Minor skew (up to about 5 degrees) is corrected cleanly; severe skew should ideally be corrected by rescanning.
• Background removal: Reduces the grey or cream background that is common when scanning yellowed or coloured paper, improving contrast for OCR and on-screen readability.
• Despeckle: Removes random pixel noise from the scanned image, reducing file size and improving OCR accuracy.

These options are configurable in the scan settings dialog and in the preset editor. For high-volume archival scanning, test each enhancement on representative samples before committing to them for a full batch.

Configuring Presets

Acrobat's scan presets let you save a named configuration of scanner settings, output options, and post-processing steps so you do not have to reconfigure everything for each scanning session.

Creating a Preset

1. In the Scan a Document dialog, click New Preset.
2. Name the preset descriptively — for example, A4 Archive 300dpi B&W or Letter Colour Forms.
3. Configure all settings: scanner, paper size, resolution, colour mode, duplex, image enhancements, and OCR options.
4. Save the preset.

Useful presets to configure for common scenarios include: a black-and-white 300 dpi preset for routine correspondence, a colour 300 dpi preset for mixed-content documents, and a 600 dpi greyscale preset for technical drawings or archival material.

Applying OCR Automatically After Scanning

Acrobat can run OCR immediately after each page is scanned, so the output PDF is already searchable when you save it — no separate OCR step required.

In the scan preset settings, enable Make Searchable (Run OCR) and select your preferred output type (Searchable Image is recommended for most use cases) and document language. With this option active, Acrobat processes each scanned page through its OCR engine and embeds the recognised text layer before saving.

For more detail on OCR output modes and accuracy considerations, see our guide on OCR in Adobe Acrobat.

Recommended Settings for Different Use Cases

Long-Term Archiving

• Resolution: 300 dpi (or 400–600 dpi for fine print)
• Colour mode: Black and white for text; greyscale or colour for mixed content
• OCR: Enabled, Searchable Image output
• Format: PDF/A-2b or PDF/A-3b (see below)

Email and Digital Distribution

• Resolution: 150–200 dpi
• Colour mode: Greyscale or black and white
• Compression: High JPEG quality for images, JBIG2 for bitonal
• OCR: Optional but recommended for searchability
• Target size: Under 1 MB per page where possible

Screen Viewing Only

• Resolution: 150 dpi
• Colour mode: As appropriate to content
• OCR: Enabled for searchability

File Size Implications of Scan Settings

Scan settings have a very significant impact on output file size. As a rough guide for an A4 page of typed text:

• 300 dpi black and white (JBIG2 compression): approximately 20–50 KB per page
• 300 dpi greyscale (JPEG compression, medium quality): approximately 100–200 KB per page
• 300 dpi colour (JPEG compression, medium quality): approximately 150–350 KB per page
• 600 dpi black and white: approximately 60–120 KB per page
• 600 dpi colour: approximately 500 KB–1 MB per page

For high-volume scanning, choosing the right settings is essential. A 1,000-page archive scanned at 300 dpi black and white might be 30–50 MB; the same archive scanned in colour at 600 dpi could exceed 500 MB. Use Acrobat's PDF Optimizer (under File > Save As Other > Optimized PDF) to reduce file size after scanning if needed.

Scanning and PDF/A Archival Standard

For documents intended for long-term digital archiving, the PDF/A standard is the appropriate output format. PDF/A is an ISO-standardised subset of PDF that prohibits features incompatible with long-term preservation — such as encryption, external dependencies, and proprietary compression — and requires that all fonts and colour profiles be embedded.

When scanning for archival purposes, configure Acrobat to save the output as PDF/A. In the Scan a Document dialog, set the PDF Output Style to Searchable Image (Exact) and save as PDF/A-2b or PDF/A-3b using File > Save As > PDF/A. Run a Preflight check after saving to confirm compliance.