PDF Text Extraction: A Technical Guide to Copying Text from PDF
This article explains the principles of PDF text extraction, handles PDF documents of no more than 200 pages, and helps you resolve the issue of messy formatting when copying text from PDF.
Diperbarui 2026-08-11
Separate Architecture of PDF Text Layer and Visual Rendering
PDF adopts a storage architecture that separates the text layer and visual rendering. The text layer stores character encoding and coordinate information, while visual rendering is responsible for outputting text styles on the screen.
When users copy text from PDF, most PDF readers output content in the storage order of the text layer by default. This order often differs from the user's visual reading order, which leads to messy formatting in the copied result.
StructuredText Reorders Text by Visual Blocks
The PDF text extraction tool of OKfmt uses the StructuredText algorithm. It first parses the PDF text layer to obtain coordinate and character information of all text, then divides independent visual blocks based on coordinate ranges.
The algorithm sorts the divided visual blocks in top-to-bottom, left-to-right order, then splices the text within all blocks, and finally outputs editable text that conforms to users' reading habits.
Comparison of Extraction Effects for Different Types of PDF
Native PDF and scanned PDF have different internal structures, leading to obvious differences in extractability. The following is a specific comparison of the two types of PDF.
| PDF Type | Extractability Description |
|---|---|
| Native PDF | Contains a text layer, and editable text can be extracted via the StructuredText algorithm |
| Scanned PDF | Only contains bitmap content, has no text layer, and cannot extract text directly |
Common Use Cases and Processing Limit for Extracted Text
The extracted plain text can be used in many scenarios, including full-text search of document content, content input for batch translation, and secondary editing and organization of original PDF content.
OKfmt's PDF text extraction tool currently sets the single-file processing limit to 200 pages. Files exceeding this limit cannot be processed, but you can split the file and process it in batches.
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Why cannot scanned PDF extract text directly?
Scanned PDF is a document spliced from bitmaps, and does not contain an editable text layer. It requires text recognition via OCR first. The current tool does not provide OCR services, so extraction is not possible.
Can the extracted text be used for translation?
The extracted text is plain editable text, which can be copied in batches to various translation tools as translation input. The specific word limit is subject to the current public announcement on the official website of the corresponding translation tool.
How to handle a PDF with more than 200 pages?
You can first use a PDF splitter to split the original file into multiple files of no more than 200 pages, then use this tool to extract text from each split file separately.