How much can you compress a PDF without visible quality loss?

Step by step

1. 1Identify the PDF type: mostly text, mixed (text + photos), or scan/image-heavy.
2. 2Run Keep text first and note the new size — this is your “free” win when structure was bloated.
3. 3If still too large, try Target size at 150 DPI-equivalent quality and inspect a page with small type.
4. 4Only push toward 100 DPI or Max shrink High when email/chat limits leave no choice.
5. 5Record before/after sizes for your own recurring templates (invoices, lecture scans) so the next time is one click.

Text-heavy PDFs

Expect modest savings from Keep text — often enough for email if the file was poorly exported. Visual quality should be unchanged because pages are not rasterized.

If Keep text barely moves the needle, the PDF was already lean; further “compression” requires deleting pages or accepting image re-encode elsewhere.

Mixed and scan-heavy PDFs

Photos and scans dominate byte count. Re-rendering around 120–150 DPI is where screen readability usually remains acceptable; print posters and fine art are the exception.

Target size that demands extreme shrinkage will hit the 50 DPI floor and tell you when the number is unreachable — treat that as a signal to split rather than destroy the page.

How to reproduce on your files

Use Compress PDF on mypdf.space with the same sample set each semester or quarter. Log original size, Keep text size, and the first Target size that still looks acceptable on your phone.

That personal table beats any generic “90% smaller” claim — and the experiment never needs to leave your laptop.

Tools used here

• Compress PDFShrink PDFs locally — keep selectable text by default, or max-shrink with a searchable overlay.
• Split PDFExtract a page range or split into individual pages. Free, private, no upload.
• OCR PDFMake scanned pages searchable with local browser OCR (Tesseract). Best-effort — English by default.
• Delete pagesRemove specific pages by number. The rest stays untouched.
• Grayscale PDFConvert pages to grayscale for printing — searchable text overlay kept when available.