What to do if multiple scanned contract PDFs are gray and unclear? Method for batch binarization to enhance text

When scanning contracts, agreements, and archival documents, image-based PDFs with heavy gray backgrounds are often generated, where the text is not dark enough and the background is not clean enough, affecting readability and printing. This article introduces how to use HeSoft Doc Batch Tool in a PDF tool to apply the "Make text in PDF images clearer" feature, batch add PDF files, enable text sharpness binarization, set appropriate parameters, and then uniformly output the processed clear files. It is suitable for office scenarios that require processing multiple scanned contracts, supporting documents, and archived files at once.

Many companies, when organizing historical contracts, service agreements, and approval documents, scan paper files into PDFs for storage. However, the scanned PDFs are often far from ideal: the page background leans gray, edges have shadows, paper texture is visible, and text appears blurry; if the document was photographed by a phone before conversion, issues like uneven lighting and dark backgrounds can also arise. A single file can be handled with some effort, but if a folder contains many scanned PDFs, editing and exporting them one by one becomes extremely inefficient, repetitive work.

This article discusses how to make text in multiple scanned contract PDFs that are gray and unclear clearer in a batch process. We will use the PDF batch processing feature in " HeSoft Doc Batch Tool ", specifically the "Make text on PDF images clearer" module, to uniformly process multiple scanned PDFs. The processed pages will have backgrounds closer to white and text closer to black, making them more suitable for reading, printing, archiving, and external sending.

Applicable Scenarios: Batch Scans, Contract PDFs, Archival PDFs Can All Be Processed This Way

This method is especially suitable for image-based PDFs. An image-based PDF refers to a PDF where the page content essentially comes from scanned or photographed images; the text is not editable but part of the image. Contract scans, stamped agreements, paper forms, archival copies, documentary evidence, and photocopies of old documents are all very typical use cases.

In office workflows, gray scanned PDFs cause several common problems. First, poor reading experience, especially with long contracts or multi-page archives, as the gray background strains the eyes more easily. Second, poor print quality, where the gray background might be printed, wasting toner and affecting the formal appearance of the document. Third, after uploading to a business system, reviewers might request a resubmission because the pages are unclear. Fourth, when file volumes are high, manually adjusting parameters like brightness, contrast, and sharpening for each file is very inefficient and prone to inconsistent results across files.

The value of HeSoft Doc Batch Tool lies in turning this repetitive operation into a unified process: first batch-import files, then uniformly set the sharpening effect, and finally batch-output the results. For roles in administration, HR, legal, finance, and archive management, this batch processing capability can significantly reduce time spent on mechanical tasks.

Effect Preview: From Gray-Background Scans to Clear Black-and-White Documents

First, look at the PDF page before processing. The contract document in the screenshot is a typical scan, with an overall gray background on the page; both left and right pages show scanning shadows and paper texture. While the main text is still legible, the contrast between the black text and the gray background is insufficient, giving an overall impression of being old and dark. If such a file is printed directly, the gray background might affect the output quality.

Now look at the processed result. The page background is visibly cleaner, the gray texture is greatly reduced, the body text is darker, and information like titles, paragraphs, and numbering is much easier to read. For contract PDFs primarily containing text, this black-and-white sharpening process makes the file closer in appearance to a standard electronic document.

It should be noted that the processing effect is related to the original scan quality. If the original image only has a gray background and the text is still intact, the sharpening effect is usually quite noticeable; if the original image is already severely blurred, the text is incomplete, or the resolution is very low, processing can only improve contrast and cannot magically restore fully lost details.

Operating Steps: Batch Processing Gray Scanned PDFs to Be Clearer

Below, we'll explain the steps in actual operating order using interface screenshots. The entire process can be understood in four stages: select function, import files, set effects, save and start processing.

Step One: Find "Make text on PDF images clearer" in PDF Tools

After launching " HeSoft Doc Batch Tool ", first look at the left navigation bar of the software. In the screenshot, the left side has categories like "Home", "Task Flow", "All Tools", "File Name", "Folder Name", "File Organization", "Word Tools", "Excel Tools", "PowerPoint Tools", and "PDF Tools". Since the processing target this time is PDF files, click "PDF Tools".

After entering the PDF tools list, find "Make text on PDF images clearer". The description on this feature card indicates it's for batch adding various effects to images in scanned PDFs to make the image text clearer. This description corresponds perfectly with our need here: we are not converting PDF formats, nor encrypting or stamping, but improving the readability of image text in scanned PDFs.

Operational Goal: Enter the correct PDF image enhancement feature, avoiding conversion or security features.

Expected Result: Open the "Make text on PDF images clearer" task page and enter the file selection process.

Step Two: Add PDFs in Batch to Create the Task List for Processing

On the feature page, you can see "Add File" and "Import files from folder" buttons at the top. For multiple scanned contract PDFs, if the files are scattered, you can use "Add File" to select them; if the files are already organized in one folder, "Import files from folder" is recommended, as this allows importing the entire batch of PDFs at once, reducing repetitive selections.

After importing, the files will be displayed in the table. The screenshot shows multiple records, with filenames ranging from service contract - 01.pdf to service contract - 07.pdf, the extension is pdf, and information such as file path, creation time, and modification time is displayed. The summary at the bottom shows the record count as 7, indicating there are 7 PDF files waiting to be processed in the current task.

Before batch processing, it is recommended to carefully check the list: confirm the file count is correct, the file path is the target folder, and no PDFs that don't need processing were accidentally included. If incorrectly added files are found, use the delete operation on the right side of the list to remove them. Buttons like "Filter" and "Sort" can also be seen on the interface, which are convenient for managing records when there are many files.

Operational Goal: Gather all scanned PDFs that need sharpening into a single batch processing task.

Expected Result: After confirming the pending file list is correct, click "Next" at the bottom.

Step Three: Enable "Text Clarity (Binarization)" and Adjust to Suitable Intensity

After entering "Set processing options", you can see the effect setting area. The screenshot shows several selectable options, including "Text Clarity (Binarization)", "Brightness", "Contrast", "Sharpening Degree". The focus of this processing is to make the text darker and the background whiter for gray-background scanned PDFs, so prioritize enabling "Text Clarity (Binarization)".

The function of binarization is to distinguish the scanned image, which originally contains many gray levels, into two types of areas: background and text. The background area will be closer to white, and text and lines will be closer to black. For scanned documents like contracts, agreements, manuals, and forms that are black text on white paper, it can usually quickly improve the problem of "grayish, dark, and insufficiently dark text".

The slider in the screenshot shows around 45%, with the ends of the slider bar labeled "Pure White" and "Pure Black". This means users can adjust the processing intensity based on the condition of the original files. Generally speaking, the grayer the background and the heavier the shadows, the higher you can try setting the processing intensity; but if it's too high, fine text, light lines, handwritten signatures, or light-colored stamps might be affected. Therefore, it is advisable to test with one or two representative PDFs first, then apply the same settings to the entire batch of files.

The "Brightness", "Contrast", and "Sharpening Degree" switches in the screenshot are not enabled, so this article does not consider them necessary steps. The advantage of this is a simpler process, which is also more suitable for most scanned PDFs dominated by black-and-white text. If you encounter special files later, you can experiment with other effects based on the actual situation.

Operational Goal: Enhance text and background contrast through binarization to make gray-background scans clearer.

Expected Result: After completing the text clarity settings, click "Next" to continue.

Step Four: Set the Output Location, Keep Original Files for Comparison

As seen from the progress bar, after processing options comes "Set save location". When batch processing PDFs, directly overwriting original files is not recommended. A safer approach is to create a new output folder and save the processed PDFs separately. For example, keep the original files in a "scanned copy" folder and save the processed results in a "scanned clear" or "Sharpened Output" folder. This way, even if the parameter settings are not ideal, you can always go back to the original files and reprocess them.

When setting the save location, also consider future usage scenarios. If the processed files are to be uploaded to a business system, you can output them to a fixed directory; if they need to be reviewed by a colleague, output to a shared folder; if they are for printing, you can randomly check a few copies after output to confirm the page effects and page count are correct.

Operational Goal: Specify where the processed files will be saved, while protecting the original scans.

Expected Result: Output directory setup is complete, proceeding to the final start processing stage.

Step Five: Start Processing and Check Results

The final step in the progress bar is "Start Processing". After confirming the file list, processing effects, and save location are all correct, you can execute the batch process. The software will process the PDFs sequentially according to the task list, applying the previously set text clarity effect to the scanned images and outputting new PDF files.

After processing is complete, it is recommended to open a few result files for inspection. Key inspection points include: Is the page background significantly whiter? Is the body text darker and clearer than before processing? Are page numbers, table lines, and underlines preserved? Are non-text content like signatures, seals, and notes still legible? Is the page count of the file complete? After confirming there are no issues, the entire batch of result files can be used for archiving, printing, or submission.

Operational Goal: Complete batch sharpening and verify output quality.

Expected Result: Multiple gray-background scanned PDFs are batch-processed into clearer PDF files.

Frequently Asked Questions and Processing Suggestions

1. Do I need to convert the PDF to images before processing?

No. As seen from the feature name and import list in the screenshot, this feature directly works with PDF files; you can add PDFs or import PDFs from a folder. Users do not need to first convert PDFs to image formats like JPG or PNG before processing, reducing intermediate steps.

2. Is batch processing suitable for PDFs with many pages?

Yes. The preview file in the screenshot shows the PDF has multiple pages, and the batch processing tool will execute the processing workflow on the imported PDF files. However, the more pages and the larger the file, the longer the processing time may be. It is recommended to ensure sufficient output disk space before processing a large number of files.

3. Will binarization affect color content?

The goal of binarization is to enhance the black-and-white text effect, so it is more suitable for text-based scans. If the PDF contains a lot of color photos, color charts, or content where color needs to be preserved, test it before use. For files like contract bodies, black-and-white forms, and scanned certificates, binarization typically aligns better with office needs.

4. Why is it recommended to test with a small batch first?

Scan quality varies greatly. Even if they are all PDFs, some come from scanners, some from mobile phone photos, some paper is yellowed, and some text is faint. First testing with a few sample files allows you to quickly find the suitable text clarity parameters, avoiding the situation where you process a large number of files only to find the effect is unsatisfactory.

5. Can the processed files be used for OCR recognition?

The focus of this article is on improving the visual clarity of scanned PDFs. Generally, a cleaner background and clearer text are usually conducive to subsequent OCR recognition, but the final recognition result also depends on the original resolution, text integrity, and the OCR tool itself. If there is an OCR requirement, you can complete the sharpening first, then perform a recognition test.

Summary: The Key to Batch Sharpening Gray-Background Scanned PDFs Is Choosing the Right Feature and Unifying Parameters

Scanned contract PDFs appearing gray and unclear is a very common office document problem. Traditional methods often require manually opening files one by one, adjusting images, and saving them again, which is time-consuming and makes it difficult to ensure consistent results for each file. Using HeSoft Doc Batch Tool , you can directly select "Make text on PDF images clearer" in the PDF tools, batch import multiple PDFs, enable "Text Clarity (Binarization)", and then uniformly output the processed files.

If you have a batch of gray-background scans, contract PDFs, archival PDFs, or documentary evidence that needs organizing, it is recommended to first test a text clarity effect around 45% on a few representative files and fine-tune based on the actual situation. After confirming the effect, import the entire folder into the software for batch processing. This can enhance the reading and printing quality of the PDFs and also delegate repetitive work to the office software, freeing up time for more valuable tasks like reviewing, archiving, and business processing.