8 Ways to Reduce PDF File Size (and When to Use Each)

First, find out why the PDF is large

A portal says the limit is 5 MB and your PDF is 14. Before you reach for the strongest compression setting, spend a minute finding out why the file is big. The right fix depends on the cause, and the wrong one costs you quality for nothing. Two quick checks tell you most of what you need.

Can you select the text? Open the PDF and drag across a sentence. If individual words highlight, the text is stored as text, which is tiny, and the weight is in pictures or fonts. If nothing highlights, every page is a scanned image.

How heavy is each page? Divide the file size by the number of pages. A page of typed text usually comes to a few tens of kilobytes at most. A scanned page often runs from a few hundred kilobytes to several megabytes.

Swipe the table sideways to see every column.

Eight ways to make a PDF smaller

1. Send only the pages that are needed

The cheapest megabyte to remove is one nobody asked for. If the recipient wants the signed agreement, they may not need the 40-page appendix behind it. In Split PDF, choose Extract pages, enter the pages under Selected pages, such as 1-3, 12, and save them as one new PDF. To delete a few pages from the middle instead, use Organize PDF. Both tools work in your browser, so the document stays on your device. How to extract pages from a PDF has the details.

2. Compress the images

When the weight is in pictures, this is the big win. Open Compress PDF, choose your file and keep Recommended selected. It lowers the resolution of photographs to suit screens and everyday printing, and it leaves text, links and form fields alone. The result shows the exact new size, and you can compare the original and compressed pages side by side before you download.

Choosing between the presets, and judging the result, is covered in How to Compress a PDF Without Losing Quality.

3. Compress to an exact limit

When the limit is a hard number, let Compress PDF work backward from it. It tries stronger and stronger settings until the file fits.

1. Switch to Meet a size limit.
2. Type the figure under Maximum file size and pick KB or MB.
3. Tick Preserve searchable text and document features if the text must stay searchable. Without it, the tool may turn pages into images to reach a small target.
4. Select Compress PDF. The result says Size limit met, or Target not reached along with the smallest size it could produce and how far over that is.

4. Repack without touching the images

The Lossless preset in Compress PDF rewrites the file more efficiently without changing a single pixel. It discards data that is no longer used and trims embedded fonts to the characters the document needs. Expect a modest saving, and sometimes none. It is the right choice when images must stay exact, and a sensible first try on a text-heavy file that seems larger than it should be.

5. Export again from the original file

If you still have the Word, PowerPoint or design file, a fresh export often beats compressing the PDF afterwards, because the application can shrink pictures while it still has the full-quality originals.

• Word for Windows: choose Save As, pick PDF, and select Minimum size (publishing online).
• PowerPoint: select any picture, open Picture Format, choose Compress Pictures, apply it to all pictures at a lower resolution, then export.
• PDF Logic: Word to PDF has a PDF quality setting with a Smaller file option that optimizes images during conversion.

Use Save As or Export, not a print-to-PDF driver. Exporting keeps links and bookmarks; printing to PDF can drop them.

6. Scan with lighter settings

Scanner defaults are often tuned for photographs, not paperwork. Two settings decide how big a scan is.

• Resolution. 300 dpi is plenty for text, and for OCR. Dropping from 600 to 300 dpi cuts the number of pixels to a quarter.
• Color mode. A color scan stores three values for every pixel; grayscale stores one. For black text on white paper, grayscale or the scanner’s black-and-white text mode gives a far smaller file that is often easier to read. Keep color for pages where it carries meaning, such as stamps, highlighting and charts.

If you scan with a phone, Scan to PDF has an Image quality choice of Small, Balanced or High when it builds the PDF.

7. Shrink photos before they go into the PDF

A PDF built from phone photos inherits every pixel of them. In JPG to PDF, set Output quality to Balanced or Smaller file instead of Preserve quality. For a single picture you plan to place in a document, Resize images and Compress images do the same job first; compressing versus resizing images explains which one you need.

8. Share a link, or send the document in parts

Sometimes the document really is that big. For email, upload it to a cloud drive and send a link instead of an attachment. Gmail, for example, caps attachments at 25 MB, and email encoding adds about a third to a file’s size in transit, so an attachment close to a limit may still bounce.

If a portal accepts several files, Split PDF’s Every N pages method cuts the document into equal parts. Name them so the order is obvious, such as “Part 1 of 3”.

Check the units before you trust the number

File sizes are counted in two ways. Decimal units treat 1 MB as 1,000,000 bytes. Binary units treat it as 1,048,576 bytes. Windows File Explorer uses binary units, macOS Finder uses decimal ones, and an upload form may use either.

The gap is enough to matter. A file that Windows lists as 4.9 MB is about 5.14 million bytes, which is over a 5,000,000-byte limit even though the number on screen looks safe. Compress PDF’s size limit uses decimal units, and its result panel shows the exact byte count next to your maximum.

Mistakes that cost quality for nothing

• Compressing the same file again and again. Each lossy pass works on images that are already degraded. Go back to the original and choose a stronger setting once.
• Zipping the PDF. The contents of a PDF are already compressed, so a ZIP file is rarely much smaller, and many portals will not accept one.
• Taking screenshots of pages. That turns light, searchable text into heavy pictures. The file gets bigger and stops being searchable.
• Chasing the number past readability. A file that fits the limit but cannot be read gets rejected by a person instead of a machine. If the small print is gone, send fewer pages or ask the recipient for another way to deliver the document.

If the upload still fails when the size is right, the cause is something else, such as the file type, a password or the page count. Why PDF uploads get rejected works through those.

When a desktop application is the better choice

Compress PDF takes one file at a time, up to 30 MB and 500 pages, and it uploads the file to our servers. Use a desktop application when a file is larger than that, when you have dozens of files to process, or when the document is not allowed to leave your computer. Adobe Acrobat Pro has an optimizer with separate controls for images, fonts and discarded content. On a Mac, Preview offers a quick Reduce File Size filter when you export.

Frequently asked questions

How do I get a PDF under 1 MB?

Use Meet a size limit in Compress PDF and enter 1 MB, or a little less. A few scanned pages will usually fit. A long color document may not stay readable at that size, in which case send fewer pages or rescan in grayscale.

Why is my scanned PDF so large?

Because every page is a photograph. A color scan at 600 dpi records four times the pixels of a 300 dpi scan, and three values for each pixel where grayscale records one. Rescanning at 300 dpi in grayscale is often the biggest saving available.

Does reducing file size always reduce quality?

No. Removing pages, repacking with Lossless and exporting again from the source do not degrade anything. Only image compression trades detail for size, and at moderate settings the difference is hard to see at reading size.

What is a good size for a PDF sent by email?

There is no universal number. Check your mail provider’s attachment limit and stay well below it, because the recipient’s server may have a lower one. Past about 20 MB, a shared link is more dependable than an attachment.