Fix Adobe Acrobat "PDF is Already Compressed" Error
Question details
The user is attempting to compress a PDF document to reduce its file size, but the software prevents further compression by stating the file is already optimized.
- Product
- Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Trying to reduce the file size of a large PDF or a scanned textbook for easier sharing, uploading, or storage.
- Observed behavior
- Adobe Acrobat displays a message stating that the PDF is already compressed, preventing standard file size reduction because images are already optimized or the file consists of heavy scanned images.
Before attempting to force further compression, save a duplicate copy of your original PDF document to ensure you do not permanently lose high-quality images or embedded data.
Use PDF Optimizer to Force Lower Image Quality
Manually adjust image resolution and embedded content settings to force further compression on documents that resist standard reduction.
When standard compression fails, the PDF Optimizer allows you to manually lower the pixels-per-inch (PPI) of embedded images and strip out invisible metadata. Note that this method will result in a noticeable drop in image clarity, especially for scanned documents.
Go to File > Save as Other > Optimized PDF in the Adobe Acrobat top menu.
In the PDF Optimizer dialog, select the 'Images' panel on the left. Set the Downsample options for Color, Grayscale, and Monochrome images to a lower PPI (e.g., 72 or 150 ppi) depending on your quality needs.
Navigate to the 'Discard Objects' and 'Discard User Data' panels on the left, and check the boxes to remove bookmarks, embedded page thumbnails, and hidden metadata.
Click OK and choose a location to save the newly optimized, smaller version of your PDF document.
Split the PDF into Smaller Files
If the PDF cannot be compressed further without severe quality loss, splitting the file into manageable sections is the best alternative for sharing and processing.
Compress or Split PDFs Easily with WPS Office
If your current software refuses to compress your file, WPS Office provides flexible, built-in PDF compression options and an intuitive page splitting tool to help you manage heavy documents effortlessly.
- 1. Open your PDF: Launch WPS Office and open the oversized PDF document you wish to optimize.
- 2. Access the Compress Tool: Navigate to the 'Tools' tab on the top ribbon and click on the 'Compress' icon.
- 3. Select Compression Level: Choose your desired level of compression based on whether you prioritize smaller file size or better image clarity, then click 'Compress'.
- 4. Alternatively Split the PDF: If you prefer splitting the document, go to the 'Page' tab, click 'Split PDF', define the page ranges, and extract them into smaller files.
Frequently Asked Questions
Why does a scanned PDF take up so much space even after compression?
Scanned PDFs are essentially large collections of images rather than text code. Each scanned page can consume 1 to 2 MB of data. Compressing them significantly requires lowering the image resolution, which may eventually render the text blurry or unreadable.
Can I compress a PDF without losing any image quality?
Lossless compression removes invisible metadata, hidden objects, and unused fonts, which can slightly reduce file size without visual loss. However, dramatic reductions in file size always require downsampling images, which leads to some quality loss.
How do I know if my PDF is already compressed to its limit?
You can check the document properties by pressing Ctrl+D (Windows) or Cmd+D (Mac). If the file is small relative to its page count (e.g., less than 50KB per text page) or was previously exported using a 'Web Minimum Size' setting, it has likely reached its maximum optimization threshold.
