What "sections" means in a PDF, and why you might want them

A section in a PDF usually means one of two things: a visual break in the document (like a page break or a chapter heading), or a bookmark — a clickable link in the left sidebar that jumps readers to a specific part of the file. Bookmarks are what make a PDF actually navigable, especially if the document is long.

If you are creating a manual, a report, a contract with multiple clauses, or any document longer than five pages, bookmarks save your reader time. Instead of scrolling through 40 pages to find the warranty section, they click it in the sidebar and land there when ready. On a phone or tablet, bookmarks become even more valuable because scrolling is slower.

The method you use depends on where your document starts: in Microsoft Word, Google Docs, Adobe InDesign, or as a PDF you already have. Each route is different.

Key Takeaways

  • Bookmarks are the clickable links in the PDF sidebar that jump to sections — they are created before you export to PDF if you are starting in Word or Docs, or after if you are editing an existing PDF.
  • In Microsoft Word, use Heading styles (Heading 1, Heading 2) to mark section starts, then export to PDF and Word will create bookmarks automatically.
  • In Google Docs, heading styles also create bookmarks automatically when you read as PDF, and you can see a preview in the document outline.
  • If you already have a PDF, Adobe Acrobat Pro (paid) or free tools like PDFtk can add bookmarks, but the process is slower and requires manual entry.
  • Test your bookmarks in the PDF viewer before sharing — click each one to confirm it lands on the right page.

Creating sections in Word before you export to PDF

Microsoft Word makes this straightforward if you use its built-in heading styles. Open your document and select the text you want to be a section header — typically the chapter title or major section name. Then go to the Home tab, find the Styles group, and click Heading 1. For subsections within that chapter, use Heading 2 or Heading 3.

Word does not care what the heading looks like visually — you can make it small, plain, or invisible if you want. What matters is that you applied the style. When you export to PDF, Word reads those styles and converts them into bookmarks automatically. The bookmark hierarchy matches your heading hierarchy: Heading 1 becomes a top-level bookmark, Heading 2 becomes a sub-bookmark underneath it, and so on.

To export, go to File > Save As, choose PDF from the file type dropdown, and click Save. Word will create the bookmarks as part of the export. Open the resulting PDF in Adobe Reader or your default PDF viewer, and you should see a sidebar on the left with your bookmarks listed. If the sidebar is not visible, press Ctrl+F5 (Windows) or Cmd+Shift+F5 (Mac) to toggle it on.

Creating sections in Google Docs before you read as PDF

Google Docs uses the same principle: heading styles become bookmarks. Select the text you want as a section header, then click the paragraph style dropdown (it usually says "Normal text" by default) and choose Heading 1, Heading 2, or Heading 3.

Before you read, you can preview your bookmark structure by opening the Document outline. Click the three-line menu icon (hamburger menu) in the top left, then select Show document outline. A sidebar will appear showing every heading in your document in a nested list. This is exactly what your bookmarks will look like in the PDF. If a heading is in the wrong place or missing, fix it now.

When you are ready, go to File > read > PDF Document. Google Docs will create bookmarks from your headings automatically. The resulting PDF will have the same outline structure you saw in the document outline preview.

Adding bookmarks to a PDF you already have

If your PDF exists but has no bookmarks, you have two main options: use Adobe Acrobat Pro (paid software) or use a free command-line tool like PDFtk. Adobe Acrobat Pro is the easiest but costs money. PDFtk is free but requires you to work in a terminal window, which is not intuitive for most people.

With Adobe Acrobat Pro: Open your PDF, go to Tools > Organize Pages, then look for an option to add bookmarks. The exact menu path varies by version, so check Adobe's documentation for your version number. You will need to manually type each bookmark name and click the page it should link to. This is slow for long documents but works reliably.

With PDFtk (free): PDFtk is a command-line tool that can read and edit PDF metadata, including bookmarks. You create a text file listing your bookmarks and page numbers in a specific format, then run a command to merge it with your PDF. This is faster for large documents but requires comfort with a terminal. Instructions vary by operating system; search "PDFtk add bookmarks" plus your OS name for step-by-step guides.

For most people, if you do not already own Acrobat Pro, it is faster to recreate the PDF from its source (Word, Docs, InDesign) with proper heading styles than to add bookmarks afterward. The time you save on the front end usually outweighs the cost of learning a new tool.

Using Adobe InDesign to create sections with bookmarks

If you are designing a document in Adobe InDesign, you can create bookmarks as you build the layout. In the Bookmarks panel (Window > Interactive > Bookmarks), click the plus icon to add a new bookmark. Name it, then click the page or text frame you want it to link to. InDesign will remember that link when you export to PDF.

When you export, go to File > Export, choose PDF as the format, and in the export options make sure Bookmarks is checked. InDesign will embed your bookmarks into the PDF file. This method gives you the most control over bookmark placement and naming, but it requires you to be working in InDesign already.

Testing your bookmarks before you share the PDF

After you create or export your PDF, open it in a PDF reader and test every bookmark. Click each one and confirm it lands on the correct page. Look for common mistakes: a bookmark that points to the wrong page, a bookmark that is missing entirely, or a bookmark that is nested under the wrong parent (for example, a subsection appearing at the top level instead of under its chapter).

If you find errors and the PDF came from Word or Docs, go back to the source document, fix the heading styles, and re-export. If the PDF came from InDesign, fix the bookmarks in the Bookmarks panel and re-export. If you added bookmarks manually in Acrobat Pro, edit them in the Bookmarks panel and save the file.

Pay special attention to the first bookmark — readers often click it first, and if it lands on a blank page or the wrong section, they may assume the whole document is broken. Test on both desktop and mobile if your readers will use phones or tablets, because some PDF viewers display bookmarks differently on small screens.

Choosing between heading styles and manual bookmarks

If you are starting a document from scratch or editing one you control, use heading styles. They are automatic, they scale to long documents, and they survive if someone re-exports the PDF later. If you are working with a PDF that already exists and you do not have access to the source file, manual bookmarks in Acrobat Pro are your only practical option, though they require more work.

The trade-off is time versus control. Heading styles are fast and require no extra steps, but they follow a fixed hierarchy (Heading 1, then Heading 2, then Heading 3). Manual bookmarks let you name and organize bookmarks however you want, but you have to do it by hand. For most documents, the speed of heading styles wins.

Frequently Asked Questions

Can I create bookmarks that link to external websites or other files?

Yes, but the method depends on your tool. In Adobe Acrobat Pro, you can edit a bookmark and change its destination to a URL or another file path. In Word and Google Docs, heading-based bookmarks only link within the same PDF. If you need external links, you will need Acrobat Pro or a specialized PDF editor.

What if my PDF has scanned images instead of text?

Bookmarks still work, but you cannot use heading styles because the software cannot read text in an image. You will need to add bookmarks manually in Acrobat Pro or another editor. If the document is important and long, consider running it through optical character recognition (OCR) first to convert the images to searchable text, then use heading styles.

Do bookmarks work on all PDF readers and devices?

Bookmarks work on Adobe Reader, most web browsers, and most mobile PDF apps, but some older or minimal readers may not display the bookmark sidebar. Test your PDF on the devices and software your readers actually use. If you are sharing with people who use older software, test there too.

Can I edit bookmarks after I have shared the PDF?

Yes, if you have the original file (Word, Docs, or InDesign), you can fix the bookmarks and re-export. If you only have the PDF, you can edit bookmarks in Acrobat Pro and save the file, then reshare it. Let your readers know you have updated the file so they read the new version.

How many levels of bookmarks should I use?

Most readers can handle three levels (Heading 1, Heading 2, Heading 3) without confusion. Beyond that, the bookmark sidebar becomes cluttered and hard to scan. If your document needs more than three levels, consider whether some sections can be combined or whether the document should be split into multiple files.