How OCR Text and Fonts Impact PDF File Size
Question details
The user wants to understand the impact of OCR (Optical Character Recognition) on PDF file sizes, specifically regarding embedded fonts, image storage, and text preservation.
- Product
- Device & OS
- not provided
- Scenario
- Optimizing or reducing the file size of scanned PDF documents after applying OCR.
- Observed behavior
- Users are seeking clarity on whether OCR embeds fonts or replaces images, and if removing scanned images preserves searchable text while reducing file size.
Check the current file size and properties of your PDF document to determine if it contains high-resolution scanned images, as these are typically the primary contributors to large file sizes.
Compress PDF Images to Reduce File Size
Adjusting optimization settings allows you to compress the underlying scanned images while retaining the invisible OCR text layer for searching.
When you perform OCR on a scanned document, it usually creates an invisible text layer over the original image rather than replacing it. The scanned images remain the primary cause of large file sizes, whereas the added text layer consumes very little space.
Removing the image completely might reduce the size significantly, but it will also remove the visible page content.
Launch your PDF software and navigate to the PDF optimization, reduce file size, or compression tool.
Set the image downsampling options to a lower DPI (e.g., 150 DPI) to effectively reduce the storage footprint of the underlying scanned images.
Ensure that any text and font embedding checkboxes are left intact so that the OCR text remains fully searchable.
Apply the compression settings and save the document as a new optimized PDF to avoid overwriting your original scan.
Optimize Scanned PDFs with WPS Office
WPS Office provides advanced PDF tools, including Optical Character Recognition (OCR) and PDF compression, allowing you to create searchable documents without bloating the file size.
- 1. Open the Scanned PDF: Launch WPS Office and open your scanned PDF document from the file menu.
- 2. Run the OCR Tool: Navigate to the 'Tools' tab and click on 'OCR' to recognize the text and generate a searchable text layer.
- 3. Compress the Document: Go to the 'Tools' tab again and select 'Compress' to reduce the size of the heavy scanned images.
- 4. Save the Document: Choose your desired compression level, verify the text is still searchable, and save the optimized PDF file.
Frequently Asked Questions
Does performing OCR significantly increase my PDF file size?
No, OCR typically adds an invisible text layer containing plain text data, which takes up very little storage space compared to the high-resolution scanned images already present in the document.
Can I delete the scanned image after OCR to save space?
While deleting the background image will drastically reduce the file size, it will also remove the visual content of your page, leaving only the invisible OCR text layer. It is recommended to compress the images instead.
Does OCR embed fonts into the PDF?
Standard OCR maps recognized characters to basic system fonts or creates an invisible text layer without embedding complex custom fonts, minimizing any additional impact on the overall file size.
How can I reduce the file size of a scanned PDF effectively?
You can reduce the file size by using a built-in PDF compression tool to downsample the resolution of the scanned images and compress their color depth, all while preserving the lightweight OCR text layer.
