PDF Editing Issues

How to Fix Files Added to a PDF in the Wrong Order When Combining

Camila Milosovich Oct 22, 2026 869 views

Question details

The user needs to maintain a strict sequential order when merging multiple documents, but files with similar names are sorting incorrectly.

How to Fix Files Added to a PDF in the Wrong Order

Product: PDF Merge Tools
Device & OS: not provided
Scenario: Selecting and combining multiple identically or similarly named files into a single PDF document.
Observed behavior: Files with similar numerical names, such as '15' and '15a', are merged in an unexpected, non-sequential order due to alphanumeric sorting rules.

Before you start

Gather all the files you intend to merge into a single folder and switch your folder view to 'Details' or 'List' so you can easily verify their current alphabetical sorting order.

Solution 1Recommended

Use Zero-Padded Numbering for File Names

Renaming your files with consistent, zero-padded numbers ensures the operating system and PDF combining software sort them in the exact numerical sequence you intend.

Computers use alphanumeric sorting by default, which evaluates numbers digit by digit. Because of this, a file named '15' might sort after '1' but before '2'. Standardizing the number of digits in your file names prevents this confusion.

Locate your files

Open the folder containing the documents you wish to combine into a PDF.

Rename the files

Right-click the first file, select 'Rename', and add leading zeros so all numbers have the same digit count (e.g., change '15' to '015' and '15a' to '015a', or use '015-01' and '015-02').

Apply sorting

Click the 'Name' column header in your folder to refresh the sorting. The files should now appear in perfect sequential order.

Combine the files

Select all the newly renamed files and drag them into your PDF combining tool to merge them.

Use Zero-Padded Numbering for File Names

Pro Tip: If you have hundreds of files, consider using a free bulk-renaming utility tool to automatically add zero-padding to all your files at once.

Solution 2

Manually Rearrange Files in Your PDF Combiner

If you only have a few files to combine, you can bypass renaming and simply arrange the file thumbnails directly within your PDF merging software.

Effortless PDF Merging

Visually Merge PDFs in the Correct Order with WPS Office

WPS Office provides a highly intuitive PDF merging tool that lets you easily import, visually arrange, and combine multiple documents into a single PDF. You can drag and drop file thumbnails to perfect your sequence without worrying about complicated renaming rules.

1. Launch WPS Office: Open the WPS Office application and click on the 'PDF' tab on the main dashboard.
2. Select Merge PDF: Navigate to the PDF toolkit and select 'Merge PDF' from the available options.
3. Import files: Click 'Add Files' and highlight all the documents you wish to combine.
4. Adjust the sequence: Use your mouse to drag and drop the file thumbnails into the exact order you need.
5. Combine and save: Click 'Merge' to instantly create and save your sequential PDF document.

Visual drag-and-drop interface for ordering files preciselyHigh compatibility with standard PDF and Microsoft Office formatsLightweight desktop application with fast processing speedsSeamless handling of large documents and bulk file batches

microsoft office alternative - wps office

Frequently Asked Questions

Why does file '10' appear before '2' when sorting on my computer?

Operating systems typically use alphanumeric sorting, evaluating characters from left to right. Since the digit '1' comes before '2', any number starting with '1' (like 10, 11, or 15) will be sorted before '2'. Using leading zeros (e.g., '02' and '10') forces the computer to sort them correctly.

Can I combine different file formats into a single PDF?

Yes. Most modern PDF editing tools, including WPS Office, allow you to select various file types—such as Word documents, Excel spreadsheets, and JPEG images—and will automatically convert and merge them into one cohesive PDF.

How do I fix the merge order if I have already created the combined PDF?

If your PDF is already merged in the wrong order, open it in a PDF editor. Open the 'Page Thumbnails' or 'Page Navigation' pane, select the pages that are out of sequence, drag them to their correct locations, and save the document.

PDF Troubleshooting