You can combine multiple files from different applications in one operation to create a single PDF. For example, you can combine word-processing files with slide presentations, spreadsheets, and web pages.

During conversion, Acrobat opens each authoring application, creates a tagged PDF, and assembles these PDFs into a single tagged PDF.

The conversion process doesn’t always correctly interpret the document structure for the combined PDF, because the files being assembled often use different formats. Because you may need to modify the reading order and tag tree of the combined document, you may need to use Acrobat Professional or Acrobat 3D to create an accessible PDF from multiple documents.

When you combine multiple PDFs into one tagged PDF, start with all untagged PDFs or all tagged PDFs. Combining tagged and untagged PDFs results in a partially tagged PDF that isn’t accessible to people with disabilities; some users—such as those using screen readers—will be completely unaware of the pages that don’t have tags. If you start with a mix of tagged and untagged PDFs, tag the untagged files before proceeding. If the PDFs are all untagged, add tags to the combined PDF after you finish inserting, replacing, and deleting pages.

Keep in mind that when you insert, replace, or delete pages, Acrobat accepts existing tags into the tag tree of the consolidated PDF in the following manner:

• When you insert pages into a PDF, Acrobat adds the tags (if any) for the new pages to the end of the tag tree, even if you insert the new pages at the beginning or the middle of the document.

• When you replace pages in a PDF, Acrobat adds the tags (if any) from the incoming pages to the end of the tag tree, even if you replace pages at the beginning or the middle of the document. Acrobat retains the tags (if any) for the replaced pages.

• When you delete pages from a PDF, Acrobat retains the tags (if any) of the deleted pages.

Pages whose tags are out of order in the logical structure tree can cause problems for screen readers. Screen readers read tags in sequence down the tree, and therefore they might not reach the tags for an inserted page until the end of the tree. To fix this problem, you’d use Acrobat Professional or Acrobat 3D to rearrange the tag tree to put large groups of tags in the same reading order as the pages themselves. To avoid the need for this advanced step, plan so that you always insert pages to the end of a PDF, building the document from front to back in sequence. For example, if you create a title page PDF separately from the PDF that contains the body of the text, add the body PDF to the title page PDF, even though the body document is much larger to process. This approach puts the tags for the body of the text after the tags for the title page, and eliminates the need for you to rearrange the tags later in Acrobat Professional or Acrobat 3D.

The tags that remain from a deleted or replaced page don’t connect to any content in the document. Essentially, they are large pieces of empty tag tree sections. These unneeded tags increase the file size of the document, slow down screen readers, and can make screen readers present confusing results. You should use Acrobat Professional or Acrobat 3D to delete the tags of deleted pages from the tag tree.

For more information, see Create merged PDFs and PDF packages.