My dad’s pension office emails him these massive PDFs. Like 8-10MB for a single letter. I don’t know what they’re doing on their end but a one-page letter shouldn’t be 8 megabytes. Anyway he needed to forward one of these to his bank and the email kept bouncing. “Attachment too large.” He called me obviously.
I compressed it from 8MB to 600KB. Same letter. Same content. Looked identical. He forwarded it and the bank got it fine. He asked me what I did and I said “made it smaller.” That was enough explanation for him.
How I do it
convertkr.com/compress-pdf. Drop the PDF. Pick quality level. Download the compressed version.
Quality levels — this is the only decision you have to make:
Medium is what I pick 90% of the time. Cuts the file size by 60-70% and you honestly can’t tell the difference unless you’re zooming in with a magnifying glass. My dad’s 8MB letter went to 600KB on Medium. Still perfectly readable.
Low is for when you really need the smallest file possible and don’t care that much about how it looks. I’ve used this for documents that were just text — no photos, no graphics. Text survives heavy compression better than images do. But if there are photos in the PDF, Low makes them noticeably fuzzy.
High is barely any compression. The file might go from 8MB to 6MB. Not much savings. I only use this when someone specifically says “don’t change the quality at all” and I need to shave off just enough to fit under an email limit.
Ultra — honestly I’ve never needed this. It’s there if you want almost zero compression. File size barely changes. I don’t know who this is for.
Why PDFs end up so big in the first place
This bugged me for a while. Why is a 2-page document 10MB?
Usually it’s because someone scanned the pages at insanely high resolution. A flatbed scanner set to 600 DPI produces huge image files. Stick two of those in a PDF and you’re at 10MB easy. The text isn’t the problem — it’s the images the scanner created.
Or someone embedded high-res photos. I’ve seen company brochures where each product photo is a full 12MP image. The brochure looks nice but it’s 40MB. Nobody can email that.
Or it was exported from some design software that didn’t optimize anything. I got a PDF from a designer once — 3 pages, 25MB. He’d exported from Illustrator with all the vector data, embedded fonts, and high-res linked images. Beautiful file. Totally unusable for email.
The compression actually works by
So what the tool does — and I’m simplifying — is take each page of your PDF, render it as a JPG image at whatever quality you picked, and rebuild the PDF with those optimized images. The original text layers, vector graphics, crazy high-res scans — all replaced with a sensibly-sized image.
This is why the quality slider matters. Higher quality = bigger images per page = bigger final PDF. Lower quality = smaller images = smaller PDF but things get blurry.
One side effect: after compression, the text in the PDF isn’t selectable anymore. It’s been turned into an image. For most people this doesn’t matter — they just need to view and print it. But if you need to copy text from the PDF later, keep the original uncompressed version.
Actual numbers from files I’ve compressed
I started keeping track because people always ask “how much smaller will it get?”
My dad’s pension letter — 8MB → 600KB (Medium). 92% reduction. One page, was just a bloated scan.
A friend’s university transcript — 4.2MB → 380KB (Medium). She needed it under 500KB for an online form. Cut it close but it worked.
Property documents — 22MB (12 pages of scans) → 2.8MB (Medium). This one I needed for email. 22MB wouldn’t send. 2.8MB sent fine.
A designer’s brochure — 40MB → 4.5MB (High). He wanted to keep quality since clients would see it. High quality compression still cut it by almost 90%. Good enough to email.
My brother’s assignment — 1.5MB → 1.1MB (Medium). Barely any change because it was already a small file. You can’t compress what’s already compressed. This is important to know — if a file is already small, the compressor won’t magically make it smaller.
When compression doesn’t help much
If the PDF is mostly text and not very large to begin with — like a 500KB document — compression won’t do much. Maybe saves 50-100KB. Not worth it.
If the PDF was already compressed by whatever software created it, compressing again doesn’t add much. Double compression is like squeezing a sponge that’s already been squeezed. There’s not much water left to get out.
If you need the text to remain selectable and searchable — compression turns pages into images. The text is gone as selectable content. For archival or accessibility purposes this might be a problem.
My workflow when a file is too big to email
Step 1: try Medium compression. If the file drops to under 20MB, done.
Step 2: if it’s still too big, try Low. Usually gets it small enough.
Step 3: if even Low doesn’t cut it — which only happens with really massive files — I split the PDF into two halves and send two emails. Not elegant but it works.
Step 4: if none of that works, upload to Google Drive and share the link. Sometimes the file is just too big for email and that’s okay.
But 90% of the time, step 1 is enough.
FAQ
Does it look the same after compression?
On Medium — yes, to your eyes. If you put the original and compressed side by side and zoom in 400% you’ll see slight differences. At normal viewing size? Identical. I’ve sent compressed documents to banks, embassies, universities. Nobody has ever said anything about quality.
Can I compress a password-protected PDF?
If you can open and view it, the compressor should handle it. If it needs a password to open, unlock it first.
Why did my file get BIGGER after compression?
Rare but it happens. If the original PDF was already well-optimized and small, the compression process (which renders pages as images) can actually produce a larger file. If this happens, just use the original. It was already optimized.
Got a PDF that’s too big? Open the compressor — Medium quality handles 90% of cases.