How to modify text size, color and boldness in PDF

Key points of this article

Changing the font size, color, and bolding are format adjustments, and changing the text content are two different things. First determine whether the text can be selected, and then decide which method to use.
The text in the scanned document is an image and it is not feasible to change the format directly. You should first use OCR to recognize it into editable text and check the recognition result.
Select a paragraph in the PDF editor and modify it. After modification, check the line spacing and line breaks to prevent the text from exceeding the original layout.
When there is no formatting option in the editor, you can export it to Word, change the font size, color and bolding, and then save it as PDF.
After completion, check the font size consistency, color and bolding effect, page numbers, headers and footers page by page to confirm that there are no misalignments or missed changes.

Many people get a PDF, and the content is fine, but the title is too small, the text color of a certain paragraph is too light, or they want to bold key sentences. PDF is not as easy to change the format as Word, so often you can only rearrange it or take a screenshot. This article is for those who need to fine-tune the appearance of PDF text, such as making the terms in a contract bold, changing the notes in a paper to gray, or making the title of a brochure larger.

The text size, color and boldness in PDF are format attributes, which are two types of operations like "replacing a certain word with another word". The former only changes the appearance, while the latter changes the content, so the judgment ideas are also different. After reading this article, you can first determine which method is suitable for your PDF, then modify it step by step, and finally use a checklist to check whether the result is messy.

How to change the format of text in PDF? One sentence conclusion

For PDFs that can select text, it is first to modify them directly in the PDF editor; for scanned documents that cannot select Chinese characters, do OCR first and then modify them; if the editor does not have a format option, export it to Word, modify it, and then convert it back to PDF. Please see the table below for which one to choose.

your situation	Recommended practices	reason
Text can be selected with the mouse, but only the title can be enlarged or reduced.	Select a paragraph in the PDF editor and adjust the font size directly	The text itself is editable, the scope of changes is small, and the layout is basically unaffected.
Text can be selected and you want to change a certain sentence to red or bold	After selecting the text, set the color or make it bold; if there is no corresponding option, take the export route to Word	Color and font weight belong to the format. Whether the editor supports it depends on the version you have.
The document is a scanned copy and no text can be selected.	First use OCR recognition to generate editable text, and then change the format.	The content of the scanned document is an image and cannot be modified individually without recognition.
The entire page needs to be completely redesigned, with many changes.	Export to Word, adjust in desktop productivity software, and save as PDF	Word is more suitable for batch format adjustment, and then convert to PDF after modification.
Just give the file a temporary mark	Priority will be given to comments or highlights, and the original text format will not be changed.	It saves trouble by not leaving the original text unchanged, and it is not easy to damage the layout.

Before you start: Confirm these points first

Make three judgments before taking action to avoid discovering that the method is wrong half way through the changes.

Whether text can be selected. Open the PDF and drag a section of text with the mouse. If it can be selected, the description text layer is editable; if it cannot be selected, it can only be selected in a box on the whole page, most of which are scanned documents or image PDFs.
Which part needs to be changed? Is it the title, the main text, or the small print in footnotes and tables. The smaller the scope, the more controllable the change. The text and tables usually involve a lot of attention, so try to write down the original font size before making changes.
Whether the original format needs to be retained. If the document is to be submitted, archived or printed, the layout is more important than the style, and large-scale adjustments should be made less often. Page after modification must be checked page by page.
Does the file have protection settings? PDFs with passwords or restricted editing permissions may not be modified. You need to obtain permission from the file owner first. Do not try to bypass restrictions.
Whether there is a backup. Save an original copy before making changes. If the changes are messed up, you can roll back. This step takes almost no time.

Steps to modify PDF text format in OmniDoc desktop client

The following process applies to ordinary PDFs where text can be selected. OmniDoc's PDF editor can directly modify text on paragraphs of the original document; whether the formatting options are displayed depends on the client version you are using. If there are no corresponding options, please look directly at the alternatives below.

Download and install the OmniDoc desktop client, the download address is download.omnidoc.top. After the installation is complete, open the client and enter the PDF editor.
Open the PDF file you want to modify. First, turn to the page you want to change and make sure the target paragraph is fully visible on the screen.
Select the text you want to modify in the paragraph. Select only the part that needs to be changed, do not select the entire page to avoid accidentally changing other content.
Check the editing toolbar or text properties panel to see if font size, color and bold settings are provided. If possible, just adjust it directly, such as changing the font size from four to three, or changing the color to dark red.
If you need to modify the text content itself, such as correcting typos, you can edit it directly in the paragraph, and then adjust the format after editing.
After the modification is completed, check whether the text exceeds the original line width or paragraph boundary. If necessary, fine-tune the font size or manually wrap the text.
Save it as a new file, and try to put the words "modified version" and other words in the file name to distinguish it from the original.
Check the results page by page using the checklist in the next section.

If the file is a scan, use the editor's OCR function before step 3 to recognize the text in the image as editable text, and then follow the steps above. The recognized text may have typos or line breaks. Please check the content before changing the format.

Alternative when the editor has no format options

Some versions of the editor can only change text content, but cannot adjust font size or color. You can take a detour at this time and the process is as follows.

Export the PDF to a Word file in OmniDoc. The export format can be Word.
Use desktop office software to open the exported Word file, select the text you want to change, and set the font size, color or boldness. Format adjustment in Word is more intuitive than PDF, and batch modification is also more convenient.
Check the paging and picture position of the entire document, because the layout may change after exporting and modifying, and needs to be adjusted page by page.
Use the "Save as PDF" function of the desktop office software to generate a new PDF file.
Open the new PDF and check whether the font, color and page number are normal according to the list.

The cost of this route is that the layout may change slightly, especially on pages with complex tables, formulas, and mixed graphics and text. If the layout of the original document is very complex, it is recommended that you only do this on the pages that need to be modified, and leave the rest of the pages as they are.

Check each item after completion

Don’t be in a hurry to send or submit after making changes. Read it item by item.

Check items	How to see	What to do if there is a problem
Is the font size uniform?	Titles at the same level or similar paragraphs should have the same font size	Reset according to the same level text of the original document
Is the color clear?	Look at it both on the screen and in the print preview. Don’t make the light text too light.	Change to a darker color, or change back to black
Is the bolding appropriate?	Bold only the parts that need to be emphasized to avoid making the entire paragraph bold	Remove redundant bolding and keep keywords
Line breaks and layout	Check whether paragraphs exceed the page margins and whether tables and pictures are squeezed	Fine-tune font size, remove extra spaces or manually wrap lines
Page numbers and headers and footers	Turn to the first, middle and last pages to see if the page numbers are correct	Check whether the header and footer have been changed by mistake and re-export if necessary.
OCR recognition content (if any)	Compare the original paragraph by paragraph, paying attention to numbers, punctuation and proper nouns	Manually correct typos, important content needs to be manually checked word for word

When checking, you can open the new file and the original side by side and compare them page by page. Minor deviations may occur in machine recognition and format conversion. Important content must be reviewed manually before formal submission.

❓ Frequently Asked Questions (FAQ)

1. Can the text size of the scanned PDF be directly changed?

Generally it cannot be changed directly. The text in the scanned document is an image and cannot be selected. You need to use OCR to identify it as editable text and then adjust the format. After identification, check the content, especially numbers and proper nouns.

2. What is the difference between modifying PDF text color online and using desktop software?

Online tools can usually be operated by uploading files and are suitable for occasional changes; desktop software can handle larger files and is more convenient for checking the layout. When choosing an online tool, look for file size limits, whether it is watermarked, privacy terms, and whether typesetting will be retained after modifications. When contracts or undisclosed information are involved, it is recommended to use the desktop version first.

3. What should I do if the paragraph layout is messed up after changing the font size?

First undo this change and compare the line widths of the original file and the modified version. You can make the font size smaller, or delete extra spaces in the paragraph, and then manually adjust the line breaks. If the page structure is complex, you can only change this paragraph without affecting the entire page.

4. The text in the PDF looks very thick after being bolded. Is it a font problem?

In most cases, the font itself does not have a bold version, and the software uses strokes to simulate bolding, which makes it visually thicker or fainter. Changing a font, or switching to color and size for emphasis, often produces a cleaner effect.

5. If you export Word and then convert it back to PDF, will the file become larger or blurry?

File size and resolution depend on the images and fonts in the original file. If the original contains high-definition images, they may be compressed after conversion; when converting back to PDF, try to choose high-quality or print-quality export settings and compare the images to see if they are clear after the change.

📝 Summary

Determining whether the text can be selected is the first step in solving how to modify the text size, color and boldness in PDF. If you can select it, adjust it directly in the editor. OCR the scanned document first. If the editor has no format option, export it to Word and then convert it back to PDF. After the modification is completed, the font size, color, layout and identification content are checked according to the list, and then the document is truly modified.

Open OmniDoc and use the PDF editor to work with your document