Why Is My Scanned PDF Too Large to Send by Email?

TL;DR: A scanned PDF is usually too large because the copier is scanning at high resolution, full colour or an inefficient file setting. For most office documents, reducing the scan resolution to 200–300 dpi, using grayscale or black-and-white, and selecting compressed PDF can cut the file size significantly without making the document difficult to read.

If your office regularly scans contracts, invoices, reports or forms to email, the problem is usually not the email system itself. The scan settings often create more image data than the document actually needs.

Why Does a Scanned PDF Become So Large?

A scanned PDF is made from images of each page. The more detail and colour the scanner captures, the larger the file becomes.

The three biggest factors are:

• resolution

• colour mode

• file format and compression

The number of pages also matters. A 30-page colour scan at 600 dpi can become dramatically larger than the same document scanned at 200 dpi in grayscale.

What Scan Resolution Should I Use?

For most office documents, 200 to 300 dpi is usually enough.

Higher resolution captures more detail, but it also creates larger files.

Recommended resolution by document type

Document Type	Recommended Resolution
Normal invoices and forms	200 dpi
Contracts and text documents	200–300 dpi
Documents with small text	300 dpi
Photos	300–600 dpi
Technical drawings or fine detail	300–600 dpi
General scan-to-email documents	200 dpi

For ordinary office documents, scanning at 600 dpi is often unnecessary.

A simple contract does not normally need the same resolution as a photograph or engineering drawing.

Is 200 dpi Good Enough for PDF Documents?

Yes, in many cases.

For invoices, quotations, correspondence, standard contracts and internal records, 200 dpi normally provides readable text while keeping the file size manageable.

Use 300 dpi if:

• the document contains very small text

• OCR accuracy is important

• the original is faint

• you may need to print the scanned document later

• the scan includes detailed diagrams

If the document is only being emailed for viewing, 200 dpi is often the better balance.

Should I Scan in Colour, Grayscale or Black-and-White?

Colour mode can make a major difference to file size.

Black-and-white

Black-and-white produces the smallest files and is suitable for simple text documents.

Use it for:

• invoices

• forms

• typed letters

• simple contracts

• black text on white paper

However, black-and-white scanning can sometimes make stamps, signatures or faint text disappear.

Grayscale

Grayscale is a good middle option.

It keeps shades of grey and can preserve:

• signatures

• stamps

• pencil marks

• faded documents

• photographs printed in black and white

The file is usually larger than black-and-white but much smaller than full colour.

Colour

Colour creates the largest files because the scanner records colour information for every part of the page.

Use colour only when colour is important, such as:

• colour charts

• highlighted documents

• ID documents

• marketing materials

• coloured signatures or stamps

• photographs

For a 20-page black-text contract, full-colour scanning usually adds file size without adding much practical value.

Which Colour Mode Is Best for Scan-to-Email?

For most business documents, grayscale at 200 dpi is a practical default.

If the document is clean black text, black-and-white may produce an even smaller file.

Use full colour only when the colour itself contains useful information.

A good office rule is:

If removing the colour would not change the meaning of the document, you probably do not need to scan it in colour.

Does PDF Format Reduce File Size?

Usually, yes, but not all PDF settings are the same.

Many multifunction photocopiers offer several PDF options, such as:

• standard PDF

• compressed PDF

• searchable PDF

• PDF/A

• high-compression PDF

A compressed PDF or high-compression PDF is normally better for scan-to-email when available.

However, very aggressive compression can reduce image quality, so check that text, signatures and small details remain readable.

Is JPEG Smaller Than PDF?

Sometimes, but JPEG is normally more suitable for individual images than multi-page office documents.

For example:

• one scanned photograph → JPEG may be appropriate

• 15-page contract → PDF is usually better

• multiple invoices in one document → PDF is easier to manage

• documents requiring OCR → searchable PDF is usually preferable

PDF also keeps multiple pages together in one file, which is more convenient for business use.

What Is a Searchable PDF?

A searchable PDF uses OCR, or Optical Character Recognition, to recognise text within the scanned image.

This allows users to:

• search for words

• copy text

• index documents

• find information more quickly

Searchable PDF can be useful for contracts, records, invoices and archived documents.

However, OCR may add processing time and sometimes increase file size slightly depending on the copier and compression settings.

If email size is the main priority, compare the normal compressed PDF and searchable PDF options on your machine.

Why Is a 10-Page PDF Sometimes Larger Than a 50-Page PDF?

Page count is only one factor.

A 10-page PDF can be larger than a 50-page document if the smaller document was scanned using:

• full colour

• 600 dpi

• photo mode

• low compression

• detailed images or graphics

Meanwhile, a 50-page black-and-white text document scanned at 200 dpi with compression can remain relatively small.

This is why scan settings matter more than page count alone.

What Are the Best Scan Settings for Email?

For typical office documents, a useful starting point is:

Setting	Recommended Choice
Resolution	200 dpi
Colour mode	Grayscale or black-and-white
File format	PDF
Compression	Medium or high compression
OCR	Use if searchable text is needed
Duplex	Enable for double-sided documents
Blank page removal	Enable if available

These settings generally provide a good balance between readability and file size.

What If My PDF Is Still Too Large?

If the PDF is still too large after adjusting the scan settings, try reducing the size further.

1. Lower the resolution

If you scanned at 300 or 400 dpi, try 200 dpi.

2. Change colour to grayscale

A full-colour scan can be much larger than grayscale.

3. Use black-and-white for plain text

For simple documents, black-and-white often creates the smallest files.

4. Select high-compression PDF

Many office photocopiers have a compressed PDF option specifically designed for smaller electronic documents.

5. Split the document

Instead of sending one 80-page attachment, scan it into two or three smaller files.

6. Remove unnecessary blank pages

Automatic blank-page removal can help reduce file size when scanning double-sided documents.

7. Use a file-sharing link

If the document still exceeds your company's email attachment limit, upload it to an approved cloud-storage system and send a secure link instead.

Why Does Email Reject My PDF?

Email systems normally have attachment-size limits.

The exact limit depends on the email provider and your organisation's IT settings.

Even when your PDF is below the theoretical maximum, email encoding can increase the amount of data transmitted. As a result, a file that appears close to the email limit may still fail to send.

For large business documents, it is better to leave some margin rather than trying to send an attachment at the maximum possible size.

Should I Scan Every Document at the Lowest Quality?

No.

The goal is not to create the smallest possible file. The goal is to create the smallest file that still preserves the information you need.

For example, aggressive compression may cause problems if:

• small numbers become blurry

• signatures are unclear

• stamps disappear

• barcode quality is reduced

• technical details become unreadable

• OCR accuracy becomes poor

Document importance should determine the settings.

Best Settings for Common Office Documents

Invoices and receipts

Use:

• 200 dpi

• grayscale or black-and-white

• compressed PDF

This is usually enough for accounting and recordkeeping.

Contracts

Use:

• 200–300 dpi

• grayscale

• PDF or searchable PDF

Grayscale helps preserve signatures and stamps.

ID documents

Use:

• 300 dpi

• colour

• PDF or JPEG

Colour may be important for identification details.

Financial reports

Use:

• 200–300 dpi

• grayscale

• PDF

If the report contains colour-coded charts, use colour only when necessary.

Drawings and diagrams

Use:

• 300 dpi or higher where required

• grayscale or colour depending on the original

• PDF

Fine detail is more important here than minimum file size.

Can a Photocopier Automatically Compress Scanned PDFs?

Many modern multifunction photocopiers include scan compression features.

Depending on the model, settings may be called:

• compact PDF

• high-compression PDF

• reduced-size PDF

• slim PDF

• scan compression

• optimised PDF

If your staff regularly struggles with oversized attachments, it may be worth setting a smaller scan-to-email profile as the office default.

For example:

Office Email Scan

• 200 dpi

• grayscale

• compressed PDF

Then staff can select a higher-quality profile only when necessary.

Should We Create Different Scan Presets?

Yes. Scan presets can reduce mistakes and save staff time.

A practical office could create three presets:

Email Document

• 200 dpi

• grayscale

• compressed PDF

Best for everyday email attachments.

Archive Document

• 300 dpi

• grayscale

• searchable PDF

Best for records and document management.

High Detail

• 300–600 dpi

• colour

• PDF

Best for drawings, photographs and detailed originals.

This is often easier than asking every employee to adjust settings manually each time.

When Is the Problem the Photocopier Rather Than the Settings?

If the scanned file remains unusually large even with low-resolution grayscale settings, the machine configuration may need checking.

Possible issues include:

• compression disabled

• incorrect default scan profile

• firmware or software configuration

• image-processing settings

• unusual PDF mode

• OCR or archival settings forcing larger files

A technician or copier provider can review the scan profile and help optimise it for your office workflow.

What Information Should I Give the Copier Technician?

If your office keeps producing very large scanned files, provide:

• copier brand and model

• current scan resolution

• colour mode

• PDF type

• number of pages

• approximate resulting file size

• whether the issue occurs with all documents

• whether scanning is done to email, folder or USB

This helps determine whether the file size is normal for the selected settings or whether the machine needs configuration changes.

FAQ

What resolution is best for scanning documents to email?

For most office documents, 200 dpi is a good starting point. Use 300 dpi when small text, signatures or fine details need better clarity.

Does grayscale make a PDF smaller?

Yes. Grayscale normally produces a much smaller file than full-colour scanning while still preserving more detail than black-and-white.

Is black-and-white always best for small file size?

It often creates the smallest files, but it may remove faint signatures, stamps or light text. Grayscale is usually safer for mixed office documents.

Should I use PDF or JPEG for scanned documents?

Use PDF for multi-page office documents such as contracts, reports and invoices. JPEG is more suitable for individual photographs or image files.

Why is my scanned PDF still too large at 200 dpi?

Check whether the scanner is still using full colour, low compression, photo mode or a special PDF setting. If the problem continues, the scan profile may need to be reviewed by your copier provider.

In summary,

If your scanned PDF is too large to send by email, reduce the resolution first, then choose a more appropriate colour mode and PDF compression setting. For most office documents, 200 dpi, grayscale and compressed PDF provide a practical balance between file size and readability.

Do not automatically scan every document in full colour at maximum resolution. Match the scan quality to the document's purpose, and create simple office scan presets so staff can produce email-friendly PDFs without repeatedly changing settings.