Many scanned PDFs suffer from gray backgrounds, darkening, and blurred text edges due to poor lighting during shooting, copy quality, or scanning parameters, affecting reading, printing, and archiving. This article explains how to use the "Sharpen Text on PDF Images" feature in HeSoft Doc Batch Tool to batch import multiple PDF files and apply processing options like text sharpening (binarization) to make the gray image backgrounds in PDFs cleaner and text clearer. It is suitable for batch optimization scenarios such as contracts, archives, invoices, and scanned documents.
In daily office work, scanned PDFs are very common, such as scanned contracts, historical archives, stamped documents, paper bills, meeting materials, textbook copies, etc. The problem is that these types of PDFs are usually not directly generated electronic text, but consist of individual scanned images. If the lighting was insufficient during scanning, the paper was off-gray, the device resolution was low, or the original has been copied multiple times, opening the PDF will reveal obvious gray backgrounds, shadows, a watermark feel, and blurry text. A single file might be reluctantly adjustable manually, but if a folder contains dozens or hundreds of PDFs, processing them one by one becomes very time-consuming.
The core problem this article aims to solve is: how to batch-process many scanned PDF files, making the gray images clearer, bringing the page background closer to white and the text closer to black, thereby improving reading, printing, archiving, and subsequent recognition quality. Below, using HeSoft Doc Batch Tool as an example, we introduce the complete approach for batch processing using the "Make Text on PDF Images Clear" function.
Applicable Scenarios: Which PDFs are suitable for making gray backgrounds white and text clearer
This method is mainly suitable for scanned PDFs, meaning files where the PDF pages are essentially composed of images. Common scenarios include:
- Contracts, agreements, and stamped documents where scanned pages appear gray, resulting in unclear prints.
- Archival materials, historical documents, and certificate materials with uneven backgrounds and heavy shadows.
- Bills, lists, and forms where the scanned text is faint and needs to be enlarged for reading.
- Batch-received PDF scans from different devices with inconsistent clarity that need unified optimization.
- Preparing scanned PDFs for archiving, printing, or subsequent OCR recognition, aiming to improve image quality first.
It should be noted that the "clarity" referred to in this article mainly involves processing the image effect within the PDF pages, such as using binarization, brightness, contrast, sharpening, etc., to make the gray background lighter and the black text stand out more. It is not about re-entering the document, nor directly converting the PDF into Word, docx, doc, or editable text. If your goal is to edit the content, you can combine it with PDF-to-Word or OCR tools for further processing after the clarity enhancement.
Effect Preview: Obvious gray background before processing, cleaner pages after
First, look at the effect of the scanned PDF before processing. As seen in the screenshot, the page is overall grayish, especially the paper background and edge areas, which have a noticeable shadow feel. Although the text content is still legible, it is not visually clean enough, appearing dark during prolonged reading or when printed.
After processing, the PDF page background turns significantly whiter, the gray shading and scanning shadows are reduced, and the text color is closer to pure black. For documents like contracts, archives, English materials, and scanned forms, this effect is generally more suitable for reading, archiving, and printing.
From the before-and-after comparison, it's clear that the focus of processing is not to change the PDF layout, but to optimize the scanned images in the pages: a cleaner background and more prominent text edges. For batches of scanned copies, batch processing avoids inefficient operations like repeatedly opening, manually adjusting colors, and saving files individually.
Operation Steps: Using HeSoft Doc Batch Tool to batch enhance PDF image text clarity
HeSoft Doc Batch Tool is a batch file processing software designed for office scenarios, suitable for handling large numbers of PDF, Word, Excel, PowerPoint, image, text, and other files. The specific operation is explained below following the process shown in the screenshots.
Step 1: Enter PDF tools, select "Make Text on PDF Images Clear"
After opening HeSoft Doc Batch Tool , locate "PDF Tools" in the feature category on the left. The right side will display multiple PDF-related functions, such as PDF Find & Replace, PDF Add Stamp, PDF to Word, PDF to JPG Image, etc. Here, the goal is to adjust the clarity of images in scanned PDF pages, so select "Make Text on PDF Images Clear".
The purpose of this step is to enter the dedicated functional page for optimizing scanned PDF image effects. After entering, the software will guide you through a wizard-style process to complete file selection, processing option settings, save location configuration, and start processing.
Step 2: Add PDF files to be processed, suitable for importing multiple scanned copies at once
Upon entering the function page, you first arrive at the "Select records to process" step. The top right of the page provides two entry points: "Add File" and "Import Files from Folder". If only a few PDFs need processing, click "Add File" to select them individually; if a batch of scanned copies are in the same folder, it's recommended to use "Import Files from Folder", which better suits practical batch office needs.
As seen in the screenshot, multiple PDF files have been added to the list. The table shows information such as serial number, name, path, extension name, creation time, and modification time. You can confirm whether the correct files have been imported through the list, or use the action bar on the right to delete records that don't need processing. After confirming the files are correct, click "Next" at the bottom.
The expected result of this step is that all scanned PDFs needing clarity enhancement are added to the pending list, eliminating the need to open, view, or manually adjust each PDF individually, significantly reducing repetitive labor.
Step 3: Set processing options, enable "Text Clarity (Binarization)"
After entering "Set processing options", you will see the "Effects" area. In the screenshot, "Text Clarity (Binarization)" is already enabled, and the clarity ratio is set using a slider, with the example value being 45%. The left side of the slider is labeled "Pure White" and the right side "Pure Black", indicating this option performs thresholding between the white background and black text, making the gray background tend towards white and the dark content like text and lines tend towards black.
For gray-background scans, binarization is usually the most critical setting. If the value is too low, the background might retain some gray; if too high, light stamps, thin lines, and faint text might be overly darkened or lose detail. Therefore, it's recommended to start with a midpoint value like the one in the screenshot, around 40% to 50%, and then adjust accordingly based on the file quality.
Options like "Brightness," "Contrast," and "Sharpening" are also visible on the page, but their toggles are off in the screenshot. In practice, if you just want to turn the gray background white and make black text clearer, using "Text Clarity (Binarization)" first is usually sufficient; if the original PDF image is very dark or the text edges are very blurry, then consider enabling other effects as needed. To avoid over-processing, it's recommended not to set all parameters too high at once.
After completing the settings, click "Next" to proceed to save location configuration.
Step 4: Set save location and start batch processing
The process bar in the screenshot shows subsequent steps for "Set Save Location" and "Start Processing". Generally, when batch processing files, it's recommended to save the output files to a new folder, such as "Clear PDFs" or "PDFs after Gray Background Processing", to avoid overwriting the original scanned copies. The benefit is that the original files can be kept as a backup; if the parameters are not ideal for some files, you can re-adjust and process them again.
After setting the save location, continue to "Start Processing". The software will process each PDF in the list one by one, applying the clarity effect to the scanned images in each file and outputting the processed PDFs. For users needing to process multiple contracts, archives, or bills, this step represents the core value of batch office tools: configuring rules once, executing in batch, without the need to repeatedly open and manually adjust each PDF.
FAQ and Precautions
1. Is a higher binarization ratio always better?
No. The purpose of binarization is to separate a grayscale image into black and white categories as much as possible, but the background, text depth, and paper shadows differ from one scanned copy to another. If the value is too high, it might cause misjudgment of light gray content, or lead to the loss of fine lines, stamps, and handwriting. It is recommended to test with a midpoint value first and confirm the effect before batch processing a large number of files.
2. Does the processed PDF become editable text?
No. This function mainly improves the display effect of images within the PDF, making the text on the images clearer. It does not automatically convert scanned images into Word, docx, doc, or editable text. If you need to copy, search, or edit text, you will need to use OCR or PDF-to-Word related functions subsequently.
3. Why is it recommended to output to a new folder?
Scanned copies often have archival properties, and the original files need to be preserved. If you overwrite the original files directly during batch processing, recovering them can be troublesome if the parameter settings are not ideal. Saving the processed PDFs to a new directory allows you to keep both the "original version" and the "clear version," which is more suitable for office archiving.
4. Is it suitable for processing color scans?
If the main content of a color scan is black and white text with a grayish background, using text clarity processing can usually improve readability. However, if the file contains important color images, color stamps, or gradient charts, binarization might alter the color presentation. Before processing such files, it's recommended to first extract a few samples for effect testing.
Summary: Batch clearing scanned PDFs, turning repetitive processing into a one-time configuration
Scanned PDFs being gray, dark, or having unclear text is a common problem in many offices, archive management, finance, HR, and legal departments. Using the "Make Text on PDF Images Clear" function in HeSoft Doc Batch Tool , you can import multiple PDFs at once and uniformly optimize them using options like "Text Clarity (Binarization)," making gray backgrounds whiter, text blacker, and pages cleaner.
If you have a batch of scanned contracts, archive PDFs, bill PDFs, or document copies to organize, it's recommended to first select a few representative files to test parameters, then batch process the entire folder. This ensures quality results while significantly reducing repetitive work, turning a task that originally required opening and adjusting files one by one into an efficient workflow of one-time setup and batch completion.