TecnoOrange 
The bank’s form says “maximum 5MB” and your PDF weighs 23MB. You’re on your phone, no computer in sight, and the limit isn’t negotiable. This has happened to me dozens of times. Fortunately, learning how to reduce PDF size on your phone is straightforward, and there are several ways to do it without losing too much quality. Here are the best methods.
Table of contents
Table of contents
- Apps to compress PDF on Android
- Apps to compress PDF on iPhone
- Online tools to compress PDFs
- Manual techniques to reduce PDF size
- Tips to avoid heavy PDFs from the start
- Real-world use cases: when you’ll need to compress a PDF
- Common mistakes when compressing PDFs on your phone
- FAQ: Frequently asked questions
- Conclusión
Apps to compress PDF on Android
On Android you have several solid options, both apps and online tools. I’m focusing on the ones I’ve tested and that actually work.
iLovePDF (best overall option)
iLovePDF is probably the most well-known PDF tool, and its Android app is excellent. The free version lets you compress up to 2 PDFs per day without registration.
- Download iLovePDF from the Play Store
- Open the app and tap “Compress PDF”
- Select the PDF from your storage
- Choose compression level: Extreme, Recommended, or Less compression
- Tap “Compress” and wait a few seconds
- Download the result
With “Recommended” compression, I’ve reduced 20MB PDFs to 3-4MB without noticeable visual difference on pages. It’s impressive.
Pro tip: If your PDF has lots of photos, choose “Extreme compression.” If it’s text and graphics, “Recommended” is enough. Extreme compression can make photos look pixelated.
PDF Compressor (specialized for compression)
If you just want to compress PDFs and don’t need to edit them, PDF Compressor is more direct. No extra features, no complications. Select the PDF, choose quality, done.
The advantage is it works offline: you don’t need internet to compress. Useful when you’re somewhere without coverage and need to send a PDF urgently.
Apps to compress PDF on iPhone
On iOS the situation is similar, with some specific apps that work very well.
PDF Expert (most complete)
PDF Expert by Readdle is the most complete PDF app on iOS. It compresses, edits, signs, and converts PDFs. Compression is available in the free version.
- Open PDF Expert and locate your PDF
- Tap the three dots (…) next to the file
- Select “Reduce file size”
- Choose the desired quality
- Save the compressed PDF
PDF Expert’s compression is quite aggressive. I’ve seen 15MB PDFs shrink to 2MB with minimal quality loss.
Apple Files (built-in solution)
Few people know this, but iOS’s Files app lets you compress PDFs natively. It’s not as powerful as third-party apps, but works for basic compression.
- Open the Files app
- Locate the PDF
- Long-press the file
- Select “Compress”
- A ZIP with the PDF will be created
Heads up: this creates a ZIP, not a smaller PDF. For email attachments it works, but if a web form needs a specific PDF, you need a third-party app.
Heads up: The compress option in iOS Files creates a ZIP, not a smaller PDF. If the web form requires a specific PDF file, this won’t work for you.
Online tools to compress PDFs
If you don’t want to install anything, web tools work perfectly from your phone’s browser.
Best options
iLovePDF.com: Same as the app but from the browser. Upload the PDF, choose compression level, and download. No registration for basic compression.
SmallPDF.com: Similar to iLovePDF with a very clean interface. Allows 2 free conversions per day.
PDF2Go.com: Offers more compression options, including adjusting image resolution and removing embedded fonts. Ideal if you need fine control.
| Tool | Free | No registration | Daily limit | Quality |
|---|---|---|---|---|
| iLovePDF | Yes | Yes | 2 PDFs/day | Very good |
| SmallPDF | Yes | Yes | 2 PDFs/day | Good |
| PDF2Go | Yes | Yes | No limit | Very good |
| PDF Compressor | Yes | Yes | No limit | Good |
Heads up: When using online tools, you upload your PDFs to external servers. If the PDF contains sensitive data (ID, contracts, banking info), use an offline app like PDF Compressor for Android.
Manual techniques to reduce PDF size
Sometimes automatic compression isn’t enough. Here are manual tricks that can make a difference.
Reduce image resolution
Most of a PDF’s weight comes from images. If your PDF has photos at 300 DPI for print but you’re only viewing it on screen, dropping to 150 DPI cuts size in half with no visible loss.
Remove unnecessary pages
Many PDFs include cover pages, indexes, or blank pages you don’t need. Removing 5-10 pages from a 50-page PDF can reduce size by 15-20%.
Convert to PDF/A
PDF/A is an optimized PDF format designed for archiving. It’s lighter because it removes interactive elements, scripts, and external references.
Remove embedded fonts
Embedded fonts can take up significant space. If your PDF uses standard fonts like Arial or Times New Roman, removing embedded fonts reduces size without affecting display.
| Technique | Typical reduction | Difficulty | Quality loss |
|---|---|---|---|
| Compress images | 40-70% | Easy | Minimal |
| Remove pages | 10-30% | Easy | None |
| Convert to PDF/A | 10-20% | Medium | None |
| Remove fonts | 5-15% | Medium | Minimal |
Tips to avoid heavy PDFs from the start
The best way to reduce a PDF is to not make it heavy in the first place.
- Scan at 150 DPI instead of 300. For documents only viewed on screen, 150 DPI is enough.
- Use grayscale instead of color when the document doesn’t need it. Black and white PDFs weigh much less.
- Convert to JPG before including photos. PNG photos weigh more than JPG for the same quality.
- Don’t generate PDFs from Word if not necessary. Word embeds many unnecessary fonts and metadata. Use “Save as PDF” with optimization options.
Pro tip: If you use a document scanner app like Adobe Scan or Microsoft Lens, set quality to “Medium” instead of “High” for regular documents. The quality difference is imperceptible on screen, but file size drops significantly.
Real-world use cases: when you’ll need to compress a PDF
It’s not always obvious when you’ll need to reduce a PDF. After years of dealing with this, here are the scenarios where I’ve needed it most:
Bank and insurance forms. Banks typically set limits of 5MB or 10MB for document uploads. If you scan your ID front and back, bank statements, and a contract, the combined PDF can easily exceed 20MB. Compressing it before uploading saves you the error message and starting over.
Sending CVs by email. If you attach a CV with photos, portfolio, and cover letters in a single PDF, it can get quite heavy. Many recruitment systems reject attachments over 10MB. A compressed CV opens faster and gives no problems.
Sharing medical records. When you get a scanned medical report, it usually comes in high resolution. If you want to share it via WhatsApp with a family member, the document sending limit might reject it. Compressing it solves the problem instantly.
Government and administrative paperwork. Official websites typically have strict file size limits. Uploading a proof of address, a deed, or a digital certificate might require prior compression.
| Use case | Typical original size | Usual limit | Reduction needed |
|---|---|---|---|
| Bank form | 15-25 MB | 5 MB | 70-80% |
| CV with portfolio | 8-15 MB | 10 MB | 30-50% |
| Medical report | 10-20 MB | 5 MB on WhatsApp | 60-75% |
| Administrative document | 5-15 MB | 2-5 MB | 50-70% |
Pro-tip: Before sending any PDF by email or uploading it to a form, check its size by tapping the file in the Files app. If it exceeds the limit, compressing it with iLovePDF or PDF Expert will take less than 30 seconds.
Common mistakes when compressing PDFs on your phone
I made quite a few mistakes at first, and I want you to avoid them:
Applying extreme compression to text documents. Extreme compression is designed for photos, not text. If you apply maximum compression to a PDF with lots of text, letters can become illegible, especially small fonts. Always use “Recommended” for text documents.
Not checking the result. Always open the compressed PDF before sending it. I’ve had cases where compression removed transparency layers or ruined tables. The 10 seconds it takes to check it saves you headaches.
Using online tools with sensitive data. If your PDF contains your ID, bank account number, or health data, don’t upload it to a free website. Use an offline app like PDF Compressor or PDF Expert’s built-in compression on iOS.
Compressing an already compressed PDF. If you try to compress a PDF that was already compressed before, you’ll barely notice a difference and might lose additional quality. First check if the PDF already has a reasonable size.
Pro-tip: Always save a copy of the original PDF before compressing it. That way, if the result doesn’t satisfy you, you can try again with a different compression level without losing the original file.
FAQ: Frequently asked questions
Do you lose quality when compressing a PDF?
It depends on the compression level. “Recommended” or “Medium” reduces size without visible loss. “Extreme” can affect image quality, especially photos.
How much can you compress a PDF?
A text-only PDF can be compressed 70-80%. A PDF with many photos can be reduced up to 90% with extreme compression, but image quality will be affected.
Is it safe to upload PDFs to online tools?
Well-known tools (iLovePDF, SmallPDF) delete files from their servers after a few hours. Still, for PDFs with sensitive data, offline apps are better.
Which app is better for compressing PDFs: iLovePDF or SmallPDF?
iLovePDF offers more free features and better compression. SmallPDF has a cleaner interface. For pure compression, iLovePDF wins.
Conclusión
How to reduce PDF size on your phone is a skill you’ll need more often than you think. Whether for uploading documents to a bank, sending emails with attachments, or freeing up space, apps and online tools make it quick and easy. My recommendation: iLovePDF for Android and PDF Expert for iPhone. Try it next time a PDF gives you size trouble.