Why Is My PDF Still Too Large? How to Reduce PDF Size for Email

You attach a PDF, hit send, and get “file too large” – or you compress it once and it’s still too big. The fix depends on what’s inside the PDF. Below, we explain the limits you’re up against, how to tell what’s making your file heavy, and which fixes actually work. Every size in this guide comes from files we ran through PDFroo’s Compress PDF tool in Google Chrome on October 8, 2026, using public IRS and NASA documents.

Quick answer

• Photos or scans inside the PDF? Compress with the Balanced preset. Our 10.32 MB photo report dropped to 2.97 MB.
• Still too large? Use Strong, or switch to Target size and enter the size you need.
• Mostly text, like a Word export or a form? It’s probably small already. If it isn’t, it contains large images or many pages, so remove or split pages.
• Zipping barely helps. In our tests, a ZIP saved only 3.5–14%.

How big can an email attachment be?

Two things catch people out. First, the recipient’s server has a limit too, and it may be smaller than yours. Second, attachments are encoded for email transport, which Microsoft says makes a message about 33% larger (Exchange documentation). A 20 MB PDF can travel as a 26–27 MB message. If you don’t know the recipient’s limit, aim for 10 MB or less.

Step 1: Figure out what’s making the PDF big

Open the PDF and try to select a line of text. If you can, it has a text layer. If the whole page selects like a picture, it’s a scan. Then match it to the table. These are our measured results with PDFroo’s three presets:

The pattern is clear. Images are where the weight is. Light is lossless. It cleans up the file structure but never touches images, which is why it saved almost nothing on the photo and scan files. Balanced and Strong re-encode images at a lower resolution. Text, form fields and bookmarks were kept in every preset we tested. A text-only form is already compact, so no preset can shrink it much.

Step 2: Compress it

1. Open Compress PDF and add your file. Processing runs in your browser, so the file isn’t uploaded.
2. Leave Balanced selected for a first try.



3. Click Compress PDF and check the before-and-after sizes.



4. Open the result and zoom to 100%. Check the smallest text, signatures and stamps.

If you need a specific size, use Target size and type it in, for example 9000 KB for a 9 MB limit. PDFroo tries progressively stronger settings until the file fits. In our tests, the photo report hit targets of 1 MB, 500 KB and 200 KB (952 KB, 476 KB and 190 KB) with its text still selectable.

Why is my PDF still too large after compressing?

1. It’s a long scan at high resolution

Scanned pages are pure images, so size grows with every page. Our 8-page, 300 DPI scan was 13.49 MB. Strong brought it to 3.15 MB, with images at about 180 pixels per inch. A 1 MB target worked (958 KB, about 98 ppi) and so did 500 KB (451 KB, 72 ppi, still readable). We could not reach 200 KB at a readable quality. PDFroo stopped at 361 KB and said so instead of producing an unreadable file:

Scans with fewer pages are much easier. A single scanned page (1.33 MB) reached 100 KB (96 KB, about 109 ppi), and two pages (3.15 MB) reached 200 KB (194 KB). For a long scan, your options are fewer pages, splitting, or rescanning.

2. You used the Light preset

Light is lossless, so it can’t shrink images. Switch to Balanced or Strong.

3. It’s a text PDF with many pages

Fonts and text compress well already. Publication 15 only went from 1.63 MB to 878 KB even on Strong. If a text PDF is still too big for email, the answer is fewer pages, not more compression.

4. The pages don’t share the weight equally

We deleted 58 of the 59 pages in Publication 15 with Delete PDF Pages. The single remaining page, the cover, was still 998 KB. Most of that (862 KB) was one large image on the cover. Removing pages helps most when the pages you remove are the ones with photos or scans.

Fixes that help (and one that barely does)

• Remove pages you don’t need. Blank backs, instructions and duplicates can go with Delete PDF Pages.
• Split it into several emails. Split PDF turned Publication 15 into pages 1–10 (1.05 MB) and pages 11–59 (562 KB). Compress each part if needed.
• Rescan at 150–200 DPI. 300 DPI or more is overkill for a document you’re emailing. Our compressed scans at about 180 ppi (Strong) and about 98 ppi (1 MB target) were both readable on screen.
• Send a link instead. Gmail switches to a Google Drive link automatically when attachments are over 25 MB. Microsoft says OneDrive links don’t count toward Outlook.com’s 25 MB limit.
• Zipping: barely helps. PDFs are already compressed internally. We zipped our test files with standard ZIP compression. Savings were 14.4% for the W-9 form, 6.8% for the photo report, 7.6% for the scan and 3.5% for Publication 15. That rarely gets a file under a limit, and the recipient has to unzip it.

Checklist before you hit send

• Is the file comfortably under the limit (ideally 10 MB or less if you don’t know the recipient’s limit)?
• Did you open the compressed copy and read the smallest text at 100% zoom?
• Are signatures, stamps and photos still clear?
• If it’s a form, are the fields still there? (Every form field was preserved in our compression tests, except when pages had to be converted to images. PDFroo tells you when that happens.)
• Is the file name descriptive, like jane-doe-lease-signed.pdf?

Need a much smaller file for an upload portal instead? See how to compress a PDF to 100 KB or 200 KB.

How we tested

All tests ran on October 8, 2026, in Google Chrome on a desktop computer, using PDFroo’s production code. We drove the real tool interface with an automated browser and checked every output file with PyMuPDF and Poppler. Test files: IRS Publication 15 (2026), IRS Form W-9, a 4-page report built from public-domain NASA Apollo 11 photos, and an 8-page “scan” made by rendering pages of Publication 15 at 300 DPI. Your results will vary with your file. Image-heavy files shrink the most.