Other PDF Issues

How to Fix Application Freezing When Combining PDF Files

Huda Qurayshi Oct 19, 2026 869 views

Question details

The user's PDF application freezes or becomes unresponsive when attempting to merge or combine multiple files.

How to Fix Application Freezing When Combining PDF Files

Product: PDF Editor
Device & OS: not provided
Scenario: Merging multiple documents into a single PDF file.
Observed behavior: The application hangs, freezes, or crashes when combining very large, complex, image-heavy, encrypted, or unsupported file formats such as Microsoft Publisher files.

Before you start

Ensure your computer has sufficient available memory (RAM) closed out of other heavy applications, and verify that none of the files you intend to merge are password-protected.

Solution 1Recommended

Optimize and Filter Files Before Combining

Prevent application freezes by checking for unsupported formats, removing encryption, and reducing the complexity of the files you are trying to merge.

Combining large, complex, or image-heavy documents requires significant processing power. Certain file types, such as Microsoft Publisher (.pub) files, may not be natively supported for direct merging and can cause the software to hang. Additionally, encrypted files block modification attempts, leading to process failures.

Check and Convert File Types

Ensure you are not including unsupported formats like Microsoft Publisher (.pub). Convert these files to standard PDF format individually before attempting to combine them.

Remove Security and Encryption

Open any encrypted or password-protected PDFs, navigate to the security settings, and remove the password protection before adding them to the merge list.

Process in Smaller Batches

Instead of merging dozens of large files at once, break the task down. Select 5 to 10 files, combine them, save the output, and then merge the resulting batches together.

Compress Image-Heavy Files

If you are dealing with very large, image-based PDFs, use a PDF compression tool to reduce their file sizes prior to starting the combination process.

Optimize and Filter Files Before Combining

Tip for Identifying Problematic Files: If the freeze persists, try combining the files one by one. This will help you isolate the specific file that is corrupted or too complex.

Solution 2

Contact Technical Support for Investigation

If standard optimization fails, the specific files might contain errors or structural issues that require technical investigation.

Combine PDFs Smoothly

Merge PDF Files Easily with WPS Office

WPS Office offers a highly optimized, lightweight PDF toolset designed to handle merging large and complex files without freezing or heavily taxing your computer's resources.

1. Open WPS Office: Launch the WPS Office application and click on the 'PDF' tab on the home screen.
2. Access the Merge Tool: Navigate to the 'Tools' menu at the top of the interface and click on 'Merge PDF'.
3. Import Your Documents: Click 'Add Files' to select all the PDF documents you wish to combine from your local drive.
4. Arrange and Combine: Drag and drop the files to set your preferred order, then click the 'Merge' button to instantly create your combined document.

Smoothly merges large, multi-page, and image-based PDF files without lag.Fully compatible with all standard PDF formats and Microsoft Office document types.Lightweight architecture ensures lower RAM and CPU consumption during heavy tasks.Built-in file compression to easily manage massive document sizes before and after combining.

microsoft office alternative - wps office

Frequently Asked Questions

Why do Microsoft Publisher files cause the PDF merger to freeze?

Microsoft Publisher (.pub) is not natively supported by standard PDF merging engines. Attempting to merge it directly without converting it to a standard PDF first causes the software to struggle with format translation, resulting in processing errors and application freezes.

Can I combine encrypted PDF files directly?

No, encrypted or password-protected PDF files strictly restrict modifications, which includes extracting and merging pages. You must open the file, input the password, and remove the security restrictions before combining it with other documents.

Is there a limit to the number of pages I can merge at once?

While many PDF editors do not have a hardcoded page limit, merging thousands of pages or highly complex image-based files simultaneously can exhaust your system's available memory (RAM). It is highly recommended to merge massive files in smaller batches to ensure stability.

How do I fix a specific PDF file that always crashes the merge tool?

The file may be corrupted or contain overly complex vector graphics. Try 'printing' the problematic PDF to a new PDF file using a 'Print to PDF' virtual printer. This flattens the file and often removes hidden complexities that cause software crashes.

PDF Troubleshooting