Where is the PDF document comparison function and what can be compared?

Key points of this article

The PDF document comparison feature, located in the PDF editor of the OmniDoc desktop client, can be used to compare two PDF files.
Two PDFs that can select text can be directly compared; the scanned document must first use OCR to recognize the text, and the recognition result must be checked against the original.
When you do not want to upload files to the web page, the local client is more suitable; when you need to compare multiple files, you should choose another more suitable tool.
When using it for the first time, it is recommended to compare two documents with known contents first, and confirm that the results can highlight the changes you are concerned about before processing the official document.

If you have two PDFs in your hands, such as the old version and the new version of the contract, or the first draft and revised draft of the paper, you usually want to figure out two things: where to turn on the PDF document comparison function, and what it can compare with. This article answers these two questions and is suitable for people who often process PDFs on computers.

Let me start with the conclusion: The PDF editor of the OmniDoc desktop client includes a function to compare two PDFs, which can be used directly to check the differences between the two documents. The specific types of changes that can be compared must be based on the actual comparison results. The following will explain how to judge.

After reading this article, you will know where the comparison entrance is, which files are suitable for comparison, how to process scanned documents, and what common methods are available when this function is not available.

Where to open PDF document comparison? One sentence conclusion

One sentence conclusion: For two PDFs that can select text, compare them in the PDF editor of the OmniDoc desktop client first; when encountering scanned documents, do OCR first and then compare.

your situation	Recommended practices	reason
Both are PDFs where text can be selected. I want to quickly see what has been changed.	Using the desktop client PDF editor’s comparison feature	The process is centralized in one software
One of them is a scanned copy	First use OCR to identify text and then compare	The text in the scanned document is an image, and the effect of direct comparison is limited.
One is Word and one is PDF	First export Word to PDF and then compare	After unifying into PDF, the format is more consistent and easier to compare.
Just want to check a few short paragraphs	Manual section-by-section comparison	Manual verification is not expensive when the content is small
Need to compare multiple documents at once	Alternative specialized tools that support multiple files	The comparison function discussed in this article is for two documents

What are the different methods?

PDF comparison function in desktop client

Select two PDFs to compare in the client's PDF editor. It is suitable for daily modifications of contracts, reports, and papers, and the operations are concentrated in one software. The shortcomings are: the way the comparison results are presented and the types of differences that can be identified must be based on the actual interface. It is recommended to try it out with a contract of about 12 pages.

Online comparison website

General category, this type of website usually gives different results after uploading two files without installing software. However, the files need to be uploaded to the website, and contracts or unpublished manuscripts need to be kept private; many websites also have restrictions on file size and number of uses.

Document comparison of office software

Desktop office software generally provides document comparison functions, but it is mainly oriented to native document formats. Support for directly comparing PDFs is often limited, and practical use often requires converting the files to the same format first.

Manual page-by-page or text comparison

Manual comparison is direct, suitable for short lengths with few changes. If the file is long, you can export both texts as plain text and then use text comparison tools to check for additions and deletions. This method requires additional conversion steps, and layout information may be lost during export.

📊 Core Comparison

Method	Is installation necessary?	Can you directly process the scan?	Whether the file needs to be uploaded	Result in cost verification
Desktop client comparison features	You need to install the client	OCR must be done first	Usually, it is not necessary to operate it locally	Each item must be checked one by one
Online comparison website	No need	It depends on the website	Yes	Subject to the results presented
Comparison of office software documentation	Generally, it is already installed	Usually not directly supported	No need	Manual verification is required
Manually compare page by page	No need	You can watch it directly	No need	Time-consuming but intuitive
Export the text and compare it	A text comparison tool is required	OCR must be done first	No need	Layout information needs to be checked separately

🎯 Which method suits you?

If you have two PDF copies with selectable text and want to quickly check changes,

Prioritize using the desktop client's comparison feature, completing selection, comparison, and viewing within a single software.

If one of the copies is a scan

First, OCR is used to identify the text in the image, then compare, and the original is checked against the original to check for accuracy.

If the file contains sensitive content and you don't want to upload it to the webpage,

Choose a local client, or manually compare the files to avoid leaving your computer.

If you only want to check very short content

Manually compare each section without needing to install extra tools for several changes.

Steps to compare two PDFs in OmniDoc

Download and install the desktop client from download.omnidoc.top.
Open the client and enter the PDF Editor.
In the PDF editor, find the function to compare two PDFs and select the two files you want to compare separately.
If one of the samples is a scan, first use OCR to recognize the text before starting the comparison.
Review the comparison results and check each marked change item by item; For amounts involved, dates, and clauses, be sure to confirm them in the original text.
When you need to take notes, you can export the PDF as Word, Excel, or PowerPoint for further organization.

❓ Frequently Asked Questions (FAQ)

1. Can scanned PDFs also be compared?

You can first use OCR to recognize the text in the image, then compare. Identification results may be incorrect; key numbers and clauses must be cross-checked against the original.

2. What differences can be seen from the comparison results?

The specific type of difference is subject to the actual results of the client. It is recommended to first try two documents with known content and see if they can mark changes you care about, such as changes in a number or a sentence.

3. Without a comparison function, what methods can be used?

Common methods include online comparison of website and office software documents, exporting text as plain text for comparison, and manually comparing pages one by one.

4. What features does PDF comparison software have?

Common features include marking added or deleted text, page-by-page comparison, exporting discrepancy records, etc. The specific tool depends on the chosen tool.

5. Can you directly compare Word files?

This article discusses a comparison between PDFs. Word files can be exported as PDF first, then compared using the comparison function. Try to keep the same page settings during export for easier page verification.

📝 Summary

PDF document comparison feature is available in the PDF editor of the OmniDoc desktop client, suitable for comparing two PDF files. Before use, first check whether the document is a scanned copy and compare with a small sample to confirm the results meet expectations before processing the official document.

Open OmniDoc and use the PDF editor to process your files