How to Fix Unsearchable Text in PDFs with Raster Images and Vector Text
Question details
The user wants to know if a single PDF page can contain both raster images and vector text, as some text in their construction drawings is searchable while specific sheet numbers are not.
- Product
- Device & OS
- not provided
- Scenario
- Viewing or searching text within construction drawing PDFs using document management software.
- Observed behavior
- Certain portions of the PDF text are fully searchable, while other parts, such as specific sheet numbers, are unrecognized by search tools because they are rasterized images rather than true text.
Determine if the unsearchable text can be highlighted with your cursor; if you cannot select individual letters, that section is a raster image and will require OCR or re-exporting to become searchable.
Export CAD Text as True PDF Text
The most reliable way to make all text searchable is to configure the export settings in your original CAD software so that all text is preserved as vector data.
A single PDF can indeed contain text, vector graphics, and raster images on the exact same page. When text acts like an image, standard PDF readers cannot index it for searching. Fixing this at the source is the most accurate solution.
Launch your CAD or drafting software and open the original construction drawing.
Check your drawing's text properties and ensure you are using TrueType fonts, which are reliably converted into searchable text during the PDF creation process.
Navigate to the Print, Plot, or Export dialog box. Look for PDF options and ensure 'Include Text' or 'Create Searchable PDF' is enabled.
Save or publish the document. Open the newly created PDF and test the search function (Ctrl+F) on the sheet numbers.
Apply OCR to Recognize Rasterized Text
If you do not have access to the original source file, you can use Optical Character Recognition (OCR) tools to extract text from the rasterized portions of the PDF.
Easily Recognize Text in Mixed-Content PDFs with WPS Office
WPS Office provides advanced PDF tools, including a powerful OCR engine, allowing you to quickly extract text from raster images and manage complex PDFs containing both vector and raster elements without needing expensive software.
- 1. Install WPS Office: Download and install WPS Office, then open your mixed-content PDF file within the application.
- 2. Launch OCR: Go to the 'Tools' tab on the top ribbon and select 'OCR' to begin analyzing the document.
- 3. Convert to Searchable PDF: In the OCR dialog, choose the 'Convert to Searchable PDF' option to recognize the rasterized text seamlessly.
- 4. Save the Document: Once the process finishes, save the newly processed PDF to enable full text searching across the entire drawing.
Frequently Asked Questions
Why is only part of my PDF searchable?
A single PDF can contain different layers of content. Text exported directly as vector data remains searchable, while text that was flattened into an image (rasterized) behaves like a photograph and cannot be searched without processing it through OCR.
How can I tell if text in my PDF is raster or vector?
Try zooming in closely on the text. Vector text will remain crisp and perfectly smooth at any zoom level, while raster text will eventually become pixelated or blurry. Additionally, you can highlight vector text with your cursor, whereas raster text cannot be selected.
Does OCR work well on CAD construction drawings?
OCR is optimized for reading clear lines of plain text. In dense CAD drawings, background lines, intricate grids, or architectural symbols can intersect with the text, which confuses the OCR engine and makes it less reliable for recognizing isolated sheet numbers.
