How to Send a Large PDF: Compress It or Share a Link

Most PDFs are small, but scanned documents, catalogues, portfolios and technical manuals can easily reach hundreds of megabytes. This guide explains why a PDF gets so big, how to make it smaller without making it unreadable, and how to send it when it is still too large for email.

Why is my PDF so large?

Text barely takes up any space in a PDF. The size almost always comes from one of these:

• Scanned pages. Each page is a photograph. A 100-page document scanned in colour at 600 dpi can be hundreds of megabytes.
• High-resolution images. Photos placed at print resolution (300 dpi or more) in brochures and portfolios.
• Embedded fonts. Usually small, but documents using many full fonts add up.
• Saved edit history. Some editors append every change to the file instead of rewriting it, so a PDF edited many times keeps growing.

How to make a PDF smaller

Pick the method for the software you have. Always keep the original and check the compressed copy before sending — fine print and diagrams are the first things to blur.

Adobe Acrobat (paid)

File › Save as Other › Reduced Size PDF is the simplest option. For more control use Optimized PDF, where you can choose the image resolution: 150 dpi is fine for reading on screen, 300 dpi for printing.

macOS Preview (free)

Open the PDF, choose File › Export, and set Quartz Filter to Reduce File Size. It is very aggressive and can make images blurry, so check the result. If it's too rough, try Acrobat or the command-line method below.

Microsoft Word (if the PDF came from a document)

Re-export from the original instead of compressing the PDF: File › Save As › PDF, and choose Minimum size (publishing online). Starting from the source almost always gives a cleaner, smaller file.

Ghostscript (free, Windows/macOS/Linux)

For the best balance of size and quality, Ghostscript lets you choose a target:

gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=smaller.pdf original.pdf

/screen gives the smallest file and lowest image quality, /ebook is a good default for reading, and /printer keeps print quality.

Scanning? Choose better settings up front

For text documents, scan in black-and-white or greyscale at 200–300 dpi. Colour at 600 dpi produces files many times larger with no benefit for reading. Many scanner apps also offer OCR, which makes the text searchable at almost no size cost.

A word on online PDF compressors

Websites that compress PDFs work, but you are uploading the document to a third party. That's fine for a brochure; think twice for contracts, ID documents or medical records.

How to send a PDF that is still too big

If the compressed file is still over your email limit (usually 20–25 MB), send a link instead of an attachment:

1. Go to the File2Share home page and drop the PDF in. No account is needed, and files up to 50 GB are fine.
2. Under Options, add a password if the document is confidential, and set an earlier expiry if it should only be available for a short time.
3. Copy the link into your email. Send the password by a different route, such as a text message.

The recipient opens the link in any browser and downloads the original PDF, uncompressed and unchanged.

Sending many PDFs at once

Put them in one ZIP file first. The recipient gets a single download instead of a dozen, and nothing gets missed. PDFs are already compressed, so zipping won't make them much smaller; the benefit is keeping them together.

If the documents belong together — say, all the pages of an application — consider merging them into one PDF instead. Acrobat (Tools › Combine Files) and macOS Preview (drag pages from one PDF's sidebar into another) can both do it.

Confidential PDFs

Contracts, ID scans, payslips and medical records deserve more than a link:

• Password-protect the PDF itself (Acrobat: Tools › Protect › Encrypt with Password; macOS Preview: File › Export › Encrypt). The file stays protected even after it is downloaded and forwarded.
• Use a short link expiry so the file stops being available once it has been delivered.
• Send the password separately from the link.

Common problems

"The compressed PDF is blurry"

The image resolution went too low. Use a gentler setting (Ghostscript /ebook or /printer, or 150–300 dpi in Acrobat) or send the original by link instead.

"The PDF won't get any smaller"

It probably has little image content left to compress, or it's already optimised. Send it by link.

"The recipient's computer says the PDF is damaged"

The download was most likely cut short. Ask them to download it again and compare the file size with the one shown on the download page.