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Free PDF compressor

Compress PDF to 100KB

Compressing a PDF to 100 KB is the most aggressive target on this list. At 100 KB, you are working with the constraints of messaging apps, legacy systems, and embedded document fields that were designed for minimal payloads. WhatsApp document sharing works smoothly at this size. Legacy database BLOB fields and older CRM systems that store documents inline often have limits in this range. Reaching 100 KB is realistic only for short, text-only documents. A 3-page contract with no images, subsetted fonts, and stripped metadata can fit comfortably. A 20-page report with charts and photos cannot, regardless of how aggressively you compress.

Start compressing

Free. No signup. Files deleted within 1 hour on the free tier.

How it works

Your PDF is processed in an isolated, ephemeral worker sandbox — encrypted at rest with AES-256.
We apply image downsampling, font subsetting, and metadata stripping based on your selected mode.
The result is streamed back to your browser, and the working copy is auto-deleted after the download window (1 hour on the free tier, longer on paid tiers).

How to compress a PDF to 100KB

Upload your PDF

Open the SecurePDF AI Compress tool and drag your file onto the upload area. Files up to 100 MB are accepted on the free tier.

Select your compression level

Choose the mode that fits your 100KB target. Start with light compression -- if the result is still too large, switch to heavy mode (or convert color scans to grayscale first for the largest gains).

Download and verify

Click Compress, then download the result. Check that the file size is under 100KB and scroll through key pages to confirm the visual quality is acceptable.

Tips for reaching 100KB

Messaging apps like WhatsApp, Telegram, and Signal handle 100 KB documents smoothly with near-instant delivery. This size also works for documents embedded in database records, CRM systems, and API payloads where the PDF is one field among many.

Start by stripping everything non-essential: metadata, thumbnails, embedded JavaScript, form fields, bookmarks, and unused font glyphs. On a typical office PDF, this alone can reclaim 30-50 KB.
Remove all images. At 100 KB, there is essentially no room for raster content. If a logo or signature is required, use a monochrome version at 72 DPI and 50x50 pixels maximum.
Use a single font family. Each additional embedded font adds 10-30 KB even after subsetting. If the document uses three fonts, consolidating to one can save significant space.
Keep the page count under 5. Each page adds structural overhead (page tree, content streams, resource dictionaries). Shorter documents compress more efficiently.
If you absolutely need a multi-page document under 100 KB, consider splitting it into individual pages and sending them separately. Each single-page text PDF will be well under 100 KB.

Frequently asked questions

Can I compress a PDF to exactly 100 KB?

For short, text-only documents (1-5 pages), reaching 100 KB or less is straightforward. For anything with images, reaching 100 KB requires removing the images or reducing them to tiny thumbnails. Compression tools optimize quality, not exact byte counts, so you may need to iterate.

What if my file is already smaller than 100 KB?

A PDF under 100 KB is already minimal. It is likely a short, text-only document that cannot be meaningfully reduced further.

Can I send a 100 KB PDF on WhatsApp?

Yes. WhatsApp supports documents up to 2 GB, but smaller files deliver faster and load instantly for the recipient. A 100 KB PDF opens almost immediately without a loading spinner, even on slow mobile connections.

What is the smallest possible size for a PDF?

An empty, single-page PDF with no content is roughly 800 bytes to 1 KB. A single-page document with one paragraph of text and a subsetted font is typically 5-15 KB. The practical minimum for a useful document is around 10-30 KB.

Should I use ZIP compression instead of PDF compression?

ZIP will not help much here. PDFs already use internal compression (Flate/Deflate), so zipping a PDF typically saves only 5-10%. Dedicated PDF compression achieves far better results by resampling images, subsetting fonts, and restructuring internal objects.

Free PDF compressor

Compress PDF to 100KB

Start compressing

Free. No signup. Files deleted within 1 hour on the free tier.

How it works

Your PDF is processed in an isolated, ephemeral worker sandbox — encrypted at rest with AES-256.
We apply image downsampling, font subsetting, and metadata stripping based on your selected mode.
The result is streamed back to your browser, and the working copy is auto-deleted after the download window (1 hour on the free tier, longer on paid tiers).

How to compress a PDF to 100KB

Upload your PDF

Open the SecurePDF AI Compress tool and drag your file onto the upload area. Files up to 100 MB are accepted on the free tier.

Select your compression level

Choose the mode that fits your 100KB target. Start with light compression -- if the result is still too large, switch to heavy mode (or convert color scans to grayscale first for the largest gains).

Download and verify

Click Compress, then download the result. Check that the file size is under 100KB and scroll through key pages to confirm the visual quality is acceptable.

Tips for reaching 100KB

Start by stripping everything non-essential: metadata, thumbnails, embedded JavaScript, form fields, bookmarks, and unused font glyphs. On a typical office PDF, this alone can reclaim 30-50 KB.
Remove all images. At 100 KB, there is essentially no room for raster content. If a logo or signature is required, use a monochrome version at 72 DPI and 50x50 pixels maximum.
Use a single font family. Each additional embedded font adds 10-30 KB even after subsetting. If the document uses three fonts, consolidating to one can save significant space.
Keep the page count under 5. Each page adds structural overhead (page tree, content streams, resource dictionaries). Shorter documents compress more efficiently.
If you absolutely need a multi-page document under 100 KB, consider splitting it into individual pages and sending them separately. Each single-page text PDF will be well under 100 KB.

Frequently asked questions

Can I compress a PDF to exactly 100 KB?

What if my file is already smaller than 100 KB?

A PDF under 100 KB is already minimal. It is likely a short, text-only document that cannot be meaningfully reduced further.

Can I send a 100 KB PDF on WhatsApp?

What is the smallest possible size for a PDF?

Should I use ZIP compression instead of PDF compression?

How it works

How to compress a PDF to 100KB

Upload your PDF

Select your compression level

Download and verify

Tips for reaching 100KB

Frequently asked questions

Other compression targets

How it works

How to compress a PDF to 100KB

Upload your PDF

Select your compression level

Download and verify

Tips for reaching 100KB

Frequently asked questions

Other compression targets