How AFileFix's PDF compressor works

When you upload a PDF, AFileFix runs it through two compression stages and keeps whichever produces a smaller file. The first stage cleans up unused objects, subsets fonts, and re-compresses data streams. The second stage handles image-heavy content — downsampling images and re-encoding them based on the quality level you picked. If neither stage produces a smaller file, we tell you the PDF is already optimized rather than handing you a "compressed" copy that's actually the same size as the original.

This dual-stage approach matters because PDFs vary enormously in what they contain. A text-only document benefits mostly from the first stage — font subsetting, stream re-compression, and removing duplicate resources. An image-heavy document benefits more from the second stage, where image DPI and JPEG quality do the bulk of the work.

Which compression level should I pick?

AFileFix offers three levels:

Small File — Maximum compression, smallest output. Images downsampled to 72 DPI, JPEG quality 50. Best for documents you're emailing or attaching to forms with strict size limits. Visible quality reduction on images and detailed graphics — usable, not pretty.

Balanced (recommended default) — Moderate compression. Images at 120 DPI, JPEG quality 72. Good balance for most everyday use: smaller files that still look professional. This is the default, and it's the one we recommend if you're not sure.

High Quality — Light compression. Images at 150 DPI, JPEG quality 85. Modest file size reduction while preserving image fidelity. Best for documents you'll print or archive, where you'd rather have a slightly larger file than visible quality loss.

If you upload multiple PDFs, you can set the level per-file — useful when some files need aggressive compression for email while others should stay print-ready.

How much smaller will my PDF actually get?

It depends on what's inside the PDF. Some realistic expectations:

• Image-heavy PDFs (scanned documents, photo decks, image catalogs): typically 40–70% smaller at the Balanced level. Larger reductions at Small File, smaller at High Quality.
• Text-only PDFs (reports, contracts, ebooks without images): typically 10–20% smaller. There's less to compress; gains come from font subsetting and stream cleanup rather than image downsampling.
• Already-optimized PDFs (PDFs that have been through a compressor before, or ones generated by tools like LaTeX that produce tight output): AFileFix will tell you the file is already optimized and skip the download rather than handing you the same file back.

If your PDF is mostly images, expect bigger savings. If it's mostly text, expect smaller savings. There's no universal compression ratio — the file's contents determine the ceiling.

How do I compress a PDF with AFileFix?

1. Drop your PDF onto the upload area above (or click to browse and select). You can drop up to 20 PDFs at once. Each file can be up to 50 MB, with a total of 200 MB across all files in a batch.
2. Pick a compression level. Balanced is the default and works well for most use cases. If you're emailing a PDF or hitting a strict size limit, switch to Small File. If you're archiving or printing, use High Quality. For batches, you can either apply one level to all files or set each file individually.
3. Click Compress. AFileFix processes your file on our server (encrypted in transit), runs the two-stage compression pipeline, and returns the result. For a single file, you'll get the compressed PDF directly. For a batch, you'll get a ZIP file with all the compressed PDFs inside, along with size-saved info for each one.
4. Download. Single files download as PDFs; batches as ZIPs. Either way, your original PDFs and the compressed outputs are deleted from our server within minutes after processing.

Will compressing a PDF reduce its quality?

It depends on the level you pick and the content of your PDF.

Text in your PDF stays sharp at every level. Neither compression engine rasterizes text — it remains selectable, searchable, and copy-pasteable after compression. If you're worried about a contract or report becoming "blurry," text-only documents don't have that problem at any level.

Images are where quality changes happen. At Small File, images are downsampled to 72 DPI and re-encoded as JPEG at quality 50. That's noticeably worse than the original on a high-resolution photo. At Balanced, you're at 120 DPI and quality 72 — still re-encoded, but most viewers won't notice the difference on screen. At High Quality, 150 DPI and quality 85 produces output that's hard to distinguish from the source for most photos and graphics.

Fonts get subset, not removed. The compression process subsets embedded fonts (keeps only the characters actually used in the document). The PDF still renders correctly; the file just doesn't include glyph data it doesn't need.

The honest summary: at Small File, expect visible image quality loss. At Balanced, expect subtle quality loss that's invisible to most viewers. At High Quality, expect quality loss to be technically present but rarely visible.

What types of PDFs work best with AFileFix Compress?

Best results: PDFs with embedded images that haven't been heavily compressed already. Scanned documents (photo-quality scans), photo galleries inside a PDF, image-heavy presentations.

Modest results: Text-heavy PDFs without much image content. The savings come from font subsetting and stream cleanup — real, but typically 10–20%.

No results: Already-optimized PDFs. If a PDF has been through a compressor before or was generated by a tool that already produces tight output, AFileFix won't be able to reduce it further. Instead of pretending to compress it and handing you the same file, we'll tell you it's already optimized.

Not supported:

• Scanned PDFs that need OCR. AFileFix's compressor doesn't perform optical character recognition. If your scanned PDF compresses but you can't search the text afterward, the original didn't have searchable text. OCR is a separate feature (on our roadmap).
• Password-protected PDFs. You'll be redirected to AFileFix's Unlock PDF tool first. Once unlocked, you can compress the result.

Files larger than 50 MB also won't go through. If your PDF exceeds the per-file limit, try Split PDF first to break it into smaller files, then compress each.

Frequently asked questions