"File size exceeds the maximum limit" is one of the most frustrating messages on an online form. Certificates, mark sheets, ID proofs and experience letters often have to be uploaded as PDFs under 100 KB, 200 KB or 500 KB. This guide explains how to compress a PDF to a smaller size, why scanned PDFs are so large, how to scan documents correctly in the first place, and how to merge, split and convert PDFs for applications – free and without uploading private documents to a server.
Why Are PDFs So Large?
A PDF can contain text, fonts, vector graphics and images. Text-only PDFs made in Word are usually small – a few pages might be under 100 KB. The problem is scanned PDFs: every page is a full-page photograph. A page scanned at 600 DPI in colour can be several megabytes on its own, so a five-page certificate bundle quickly reaches 10–20 MB. The main ways to shrink a PDF are to reduce image resolution, use JPG compression for the page images, and convert colour to greyscale where colour is not needed.
How to Compress a PDF: Step by Step
- Open the PDF compressor and select your PDF.
- Choose a compression level – stronger compression gives a smaller file with slightly lower image quality.
- Check the new file size shown on screen.
- Download the compressed PDF and open it to make sure every page is readable.
Because the tool runs entirely in your browser, confidential documents such as bank statements and ID proofs never leave your computer or phone.
How to Compress a PDF to 100 KB, 200 KB or 500 KB
Reaching a strict limit depends on how many pages you have and how the PDF was made:
- One-page scanned certificate to under 100 KB – scan or photograph at about 150–200 DPI, in greyscale if colour is not required, then compress. This is usually enough.
- Multi-page document to under 200 KB – you may need greyscale, lower resolution, and to remove blank or unnecessary pages with Split PDF.
- Under 500 KB – most scanned documents of up to 5–10 pages reach this with moderate compression.
If the PDF is still too large after compression, the fastest fix is usually to rescan the pages at a lower resolution, as explained below.
Scan Documents Right the First Time
| Setting | Recommended for online forms |
|---|---|
| Resolution | 150–200 DPI (300 DPI only if the form requires it) |
| Colour mode | Greyscale for text documents; colour only for photos or coloured seals if required |
| Format | PDF (or JPG for single images) |
| Page size | A4, cropped to the document edges |
A document scanned at 150 DPI in greyscale is often 10 times smaller than the same page at 600 DPI in colour, and still perfectly readable on screen.
Scanning with Your Phone
You do not need a scanner. Place the document on a dark, flat surface in good daylight, hold the phone directly above it and use a scanning app or your phone's built-in document scanner (available in the Notes or Files app on many phones and in Google Drive). These apps straighten the page and increase contrast. Save as PDF, then compress if needed. Avoid shadows, fingers and folded corners, which make pages harder to read and harder to compress.
Turn Photos into a PDF
If you have photographed each page as a JPG, combine them into one PDF with JPG to PDF. Arrange the pages in order, then download. For the smallest result, resize the photos to about 1,200–1,600 pixels on the longer side before converting.
Merge and Split PDFs for Applications
- Merge PDF – many forms allow only one upload for "educational certificates". Use Merge PDF to combine your mark sheets into one file, in order, and then compress the combined file.
- Split PDF – if a form wants only the first page of a document, or each certificate separately, use Split PDF to extract the pages you need.
Tip: merge first, then compress once. Compressing each file and then merging can reduce quality twice.
Converting PDF to Word or Images
Need to edit a PDF? PDF to Word extracts the text into an editable document; it works best with PDFs created from text rather than scanned pages. To use a PDF page as an image – for example, on a website or in a presentation – use PDF to JPG.
Keeping Your Documents Private
Many free PDF websites upload your files to their servers. That is a risk for Aadhaar cards, PAN cards, passports, salary slips and bank statements. Our PDF tools process everything inside your browser using JavaScript, so your files are never sent over the internet. As an extra precaution, some people write "Submitted for [purpose] only" across a copy of an ID document before uploading it.
Password-Protected PDFs
Bank statements and e-Aadhaar PDFs are often password-protected. Most online forms cannot read locked files, and compression tools cannot process them. Open the file in a PDF reader using the password, then use the reader's "print to PDF" option to save an unlocked copy for uploading. Keep the original protected file for your own records.
Common Mistakes
- Scanning at very high resolution "for quality" – it only makes files larger.
- Uploading blurry phone photos with shadows.
- Compressing so much that text becomes unreadable – always check the output.
- Uploading the wrong document in a merged file – check the page order.
- Using unknown websites for sensitive documents.
What Size Should Each Document Be?
| Document | Typical approach |
|---|---|
| Single-page certificate or mark sheet | Scan at 150–200 DPI in greyscale; usually 60–150 KB after compression |
| ID proofs (Aadhaar, PAN, passport) | Front and back on one page if allowed; greyscale unless colour is required |
| Multi-page bank statement or salary slips | Keep only the pages requested; merge, then compress once |
| Research paper or thesis | Export directly from Word or LaTeX as PDF rather than scanning a printout |
Exporting a document straight to PDF from Word, Google Docs or LibreOffice gives a far smaller and sharper file than printing and scanning it.
Compressing PDFs for Email
Most email services limit attachments to around 20–25 MB per message, and large attachments can bounce or fill the recipient's inbox. Compress large PDFs before sending, or split a long document into parts. For very large files, share a link from cloud storage instead of attaching the file.
Always Check Before You Submit
After compressing, open the PDF and zoom in on small print such as roll numbers, dates and seals. Check the page order and count, and make sure nothing is cut off. Rename the file clearly – for example name-class10-marksheet.pdf – so you upload the right document to the right field. Keep both the original and compressed versions until your application is accepted.
Prepare All Documents Before You Start a Form
Many application portals log you out after a period of inactivity. Scan, compress and name every document before you begin, and keep them in one folder, so that uploading takes minutes rather than a rushed hour before the deadline.
Frequently Asked Questions
How do I compress a PDF to under 200 KB?
Open the PDF compressor, choose a stronger compression level and download the result. If it is still too big, rescan the pages at 150 DPI in greyscale and remove unnecessary pages.
Why is my scanned PDF so large?
Each page of a scanned PDF is a high-resolution image. Scanning at 600 DPI in colour creates very large files; 150 to 200 DPI in greyscale is enough for online forms.
Is it safe to compress PDFs online?
With our PDF tools, yes – the files are processed in your browser and never uploaded to a server.
Can I compress a PDF on my phone?
Yes. Open the PDF compressor in your mobile browser, select the file from your phone and download the smaller version.
How do I combine several certificates into one PDF?
Use Merge PDF to combine the files in the right order, then compress the merged PDF once.
Will compressing a PDF reduce its quality?
Images inside the PDF lose some detail, but text remains readable at sensible settings. Always check the compressed file before uploading.
Why won't my bank statement PDF compress?
It is probably password-protected. Open it with the password and save an unlocked copy using print to PDF, then compress that copy.
Can I compress a PDF without losing quality?
Text-based PDFs can often be made smaller with little visible change. Scanned PDFs always lose some image detail, so choose the lightest compression that meets the size limit.
What DPI should I scan documents at?
150 to 200 DPI is enough for online forms. Use 300 DPI only if the form specifically requires it.
Why does the portal say my PDF is corrupted?
The file may be password-protected, still downloading, or saved by an app in an unusual format. Open it, save an unlocked copy with print to PDF and upload that copy.
Note: File size limits and document formats differ between forms. Always check the official instructions before uploading.