Start by finding what makes the PDF large
A PDF can be large for several reasons. It may contain high-resolution photos, full-page scans, repeated images, unused pages, embedded fonts or complex graphics. A 30-page text document can be smaller than a one-page scan if the scan was saved as a huge photo.
Before looking for a compression button, open the file and identify the source. If most pages are text, the size may already be reasonable. If the pages are camera images, receipts or scanned forms, image choices will have the biggest impact.
Remove pages that do not need to be shared
The simplest reduction is removing unnecessary pages. Many documents include blank pages, cover sheets, duplicate scans, instructions or attachments that the recipient does not need. Splitting the PDF and exporting only the relevant page range can reduce size without lowering visual quality.
This is also a privacy improvement. Sending fewer pages means sending less personal information. If the recipient only needs one signed page from a larger packet, extract that page instead of sending the whole file.
Watch image resolution
Image-heavy PDFs are often large because the images are much bigger than the page display requires. A phone photo can be thousands of pixels wide. That is useful when tiny print must remain readable, but it can be excessive for a simple receipt or form.
When creating a PDF from images, crop the photo first and choose a page fit that keeps the content readable without preserving unnecessary background. If the document will only be read on screen, you usually do not need the same image detail as a print archive.
Use JPG and PNG deliberately
JPG is usually smaller for photos, scans with shadows and image-heavy pages. PNG is often sharper for screenshots, line art and pages with crisp text edges. Choosing the wrong format can either increase file size or make text look soft.
If you export PDF pages as images, use PNG when text clarity matters and JPG when the page is photo-like and file size is more important. After export, open the result and zoom into small text before deciding it is good enough.
Clean scans before rebuilding a PDF
Cropping large borders, removing duplicate photos and rotating pages before conversion can make the final PDF smaller and easier to read. A clean source image also helps OCR if you later need searchable text. Do not rely on compression to fix a poor scan; it may make a bad image smaller, but it will not make it clearer.
Practical size checklist
- Extract only the pages the recipient needs.
- Crop photos before converting them to PDF.
- Use JPG for photo-like scans and PNG for sharp text images.
- Check small text after reducing image detail.
- Keep an original high-quality copy when the document is official.
When email or portal limits are the problem
File size limits are common in email, application portals and expense systems. Before lowering quality, check the limit and the purpose of the upload. If a portal accepts 10 MB and your file is 11 MB, extracting an unnecessary instruction page may solve the problem without changing image detail. If your file is 80 MB, the source is probably image-heavy and needs a more careful cleanup.
When sending documents by email, remember that attachments can be expanded by mail systems. A file that looks close to the limit may still fail after sending. In that case, split the document into logical parts or remove pages that are not needed rather than compressing everything blindly.
What not to remove
Do not remove pages that identify the document, explain totals or contain terms connected to later pages. A shorter file is only useful if the recipient can still understand it. For invoices, keep the vendor, date, total and invoice number. For forms, keep the page that shows the applicant or account reference. For contracts, keep signature pages and clauses that are being referenced.
When not to reduce quality
Some PDFs should remain high quality: identity scans, signed contracts, medical records, legal filings and documents with small numbers or stamps. If reducing size makes the file easier to send but harder to verify, it is the wrong tradeoff. In those cases, split the file or send only the relevant pages instead of aggressively lowering image quality.