Free online utilities for PDF compression and image resizing
Reduce the file size of a PDF using practical compression settings. QuakeStar currently allows up to 7 file conversions every 2 hours.
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A PDF is a container that can hold text, fonts, vector artwork, photographs, scanned pages and other data. The largest part of many PDF files is not the text at all — it is the images embedded inside the document.
PDF compression can reduce file size by optimizing those images and other internal resources. The result depends on the document. A scanned 50-page report may contain dozens of full-page images and therefore have considerable room for compression. A PDF generated directly from a word processor may already contain compact text and efficiently compressed images, leaving much less to reduce.
That is why two PDFs of the same number of pages can have dramatically different file sizes.
A scanned PDF stores an image of each page rather than actual text. High-resolution scans can grow very quickly.
Photographs, screenshots and embedded graphics are usually the largest part of a PDF.
Some PDFs already use efficient compression. Repeated compression may shrink quality more than file size.
Higher compression generally produces smaller files at the cost of some image detail. Lower compression preserves more visual information but produces a larger result.
The right choice depends on the purpose of the document. For a PDF that will primarily be read on a screen or attached to an email, a more aggressive setting may be perfectly acceptable. For a document containing detailed diagrams, photographs or material intended for high-quality printing, use a higher-quality setting and accept a larger file.
If the document is important, keep the original. Compression is an optimization step, not a replacement for your highest-quality source file.
A normal electronically generated PDF can store a sentence as actual characters. A scanned PDF may instead store an image of the entire page.
Multiply a high-resolution page image by 20, 50 or 100 pages and the file size can grow very quickly. Scanned documents therefore often offer some of the largest potential reductions, although aggressive compression may also make fine print or photographs less clear.
If the PDF contains OCR text in addition to scanned page images, visually inspect the compressed result before deleting or archiving the original.
A small reduction does not necessarily mean the compressor failed. Your PDF may already contain:
Repeatedly compressing an already optimized PDF can eventually reduce visual quality without producing a meaningful reduction in file size.
Open the resulting file and check:
For an important document, compare the compressed copy with the original before sending it.
PDF compression is useful when:
For more detail, see How to Make a PDF Small Enough to Email and Why Is My PDF File So Large?.