Creating PDF indexes

To speed up the search process of a lengthy PDF file, you can include an index of the words in the document. This index can be searched much faster by Acrobat than by searching the actual document. The index is included in all copies of the PDF file. Users can search through PDFs with indexes just as they would with PDFs that don't have an embedded index.

Add an index to a PDF

Update or remove index in a PDF

About the catalog feature (Acrobat Pro)

You can define a specific group of PDFs as a catalog and create a unified index for that entire collection of documents. When users search the cataloged PDFs for specific information, the index makes the search process much faster.

When you distribute the collection on a CD, you can include the index with the PDFs.

You can catalog documents written in Roman, Chinese, Japanese, or Korean characters. The items you can catalog include the document text, comments, bookmarks, form fields, tags, object and document metadata, attachments, document information, digital signatures, image XIF (extended image file format) metadata, and custom document properties.

Prepare PDFs for indexing (Acrobat Pro)

To index PDFs, start by creating a folder that contains complete PDFs with electronic features like links, bookmarks, and searchable text. For scanned documents, ensure that the text is searchable. It's better to break longer documents into smaller chapter-sized files to enhance search performance. Adding information to the document properties also improves searchability.

Before indexing a document collection, set up the document structure on the disk drive or network server volume and verify cross-platform filenames. Cross-platform filenames may be truncated, making them difficult to retrieve in a search. Follow these guidelines to prevent this problem:

• Rename files, folders, and indexes using the MS-DOS® file-naming convention (eight characters or fewer followed by a three-character file extension), particularly if you plan to deliver the document collection and index on an ISO 9660-formatted CD-ROM disc.
  
• Remove extended characters, such as accented characters and non-English characters, from file and folder names. (The font used by the catalog feature doesn’t support character codes 133 through 159.)
• Don’t use deeply nested folders or paths that exceed 256 characters for indexes that will be searched by macOS users.
• If you use macOS with an OS/2® LAN server, configure IBM®LAN Server Macintosh (LSM) to enforce MS-DOS® file-naming conventions or index only FAT (file allocation table) volumes. (HPFS [high-performance File System] volumes may contain long unretrievable filenames.)
• If the document structure includes subfolders that you don’t want to be indexed, you can exclude them during the indexing process.

Add metadata to document properties (Acrobat Pro)

To make a PDF easier to search, you can add file information, called metadata, to the document properties. (You can see the properties of the currently open PDF by choosing File > Properties, and clicking the Description tab.)

When adding data for document properties, consider the following Adobe Recommendations:

• Use a good descriptive title in the Title field. The filename of the document should appear in the search results dialog box.
• Always use the same option (field) for similar information. For example, don’t add an important term to the subject option for some documents and to the Keywords option for others.
• Use a single, consistent term for the same information. For example, don’t use biology for some documents and life sciences for others.
• Use the author option to identify the group responsible for the document. For example, the author of a hiring policy document might be the human resources department.
• If you use document part numbers, add them as Keywords. For example, adding doc#=m234 in Keywords could indicate a specific document in a series of several 100 documents on a particular subject.
• Use the subject or Keywords option, either alone or together, to categorize documents by type. For example, you might use a status report as a subject entry and monthly or weekly as a keyword entry for a single document.
• If you already have specialized training in Adobe PDF, you can define custom data fields, such as document Type, document number, and document identifier, when you create the index. This is recommended only for advanced users and isn’t covered in Acrobat complete Help.

Create an index for a collection (Acrobat Pro)

When you build a new index, Acrobat creates a file with the . Pdx extension and a new support folder, which contains one or more files with .idx extensions. The IDX files contain the index entries. All of these files must be available to users who want to search the index.

See indexing options 

• Do Not Include Numbers: Select this option to exclude all numbers that appear in the document text from the index. Excluding numbers can significantly reduce the size of an index, making searches faster.
• Add IDs To Adobe PDF v1.0 Files: Select this option if your collection includes PDFs created before Acrobat 2.0, which didn’t automatically add identification numbers. ID numbers are needed when long macOS filenames are shortened as they’re translated into MS-DOS® filenames. Acrobat 2.0 and later versions automatically add identifiers.
• Do Not Warn For Changed Documents When Searching: When this option isn’t selected, a message appears when you search documents that have changed since the most recent index build.
• Custom Properties: Use this option to include custom document properties in the index; only custom document properties that already exist in the PDFs you index are indexed. Type the property, make a selection from the Type menu, and then click Add. These properties appear as a search option in the Search PDF window's additional criteria pop-up menus when you search the resulting index. For example, if you enter the custom property Document Name and choose the string property from the Type menu, a user searching the index can then search within the custom property by selecting Document Name from the 'Use These Additional Criteria' menu.

• XMP Fields: Use this option to include custom XMP fields. The custom XMP fields are indexed and appear in the additional criteria pop-up menus to be searchable in the selected indexes.
• Stop Words: Use to exclude specific words (500 maximum) from the index search results. Type the word, click Add, and repeat as needed. Excluding words can make the index 10% to 15% smaller. A stop word can contain up to 128 characters and is case-sensitive.
• Structure Tags: Use this option to make specific leaf-element tag nodes searchable in documents that have a tagged logical structure.

Catalog ReadMe files (Acrobat Pro)

It’s often a good idea to create a separate ReadMe file and put it in the folder with the index. This ReadMe file can give people details about your index, such as:

• The kind of documents indexed.

• The search options supported.

• The person to contact or a phone number to call with questions.

• A list of numbers or words that are excluded from the index.

• A list of the folders containing documents included in a LAN-based index, or a list of the documents included in a disk-based index. You might also include a brief description of the contents of each folder or document.

• A list of the values for each document if you assign document info field values.

  If a catalog has an especially large number of documents, consider including a table that shows the values assigned to each document. The table can be part of your ReadMe file or a separate document. While you’re developing the index, you can use the table to maintain consistency.

Revise an index (Acrobat Pro)

You can update, rebuild, or purge an existing index.

Catalog preferences (Acrobat Pro)

You can set preferences for indexing that apply globally to all subsequent indexes you build. You can override some of these preferences for an individual index by selecting new options during the index-building process.

In the Preferences dialog box under Categories, select Catalog. Many of the options are identical to those described for the index-building process.

Scheduled index updates (Acrobat Pro)

To automate the process of building, rebuilding, updating, and purging an index, you can use the Catalog feature along with a catalog batch PDX file (.Bpdx). This file contains a list of catalog index file paths and flags. You can schedule when and how often to automatically perform these tasks using a scheduling application like Windows® scheduler. To do this, you simply display the BPDX file in Acrobat, and Acrobat will re-create the index according to the flags in the BPDX file.

To use BPDX files, go to Preferences > Catalog and then select the check box for Allow Catalog Batch Files (. Bpdx) to re run.

Move collections and their indexes (Acrobat Pro)

You can develop and test an indexed document collection on a local hard drive and then move the finished document collection to a network server or disk. An index definition contains relative paths between the index definition file (PDX) and the folders containing the indexed documents. If these relative paths are unchanged, you don’t have to rebuild the index after moving the indexed document collection. If the PDX file and the folders containing the indexed documents are in the same folder, you can maintain the relative path simply by moving that folder.

If the relative path changes, you must create an index after you move the indexed document collection. However, you can still use the original PDX file. To use the original PDX file, first move the indexed documents. Then copy the PDX file to the folder where you want to create the index, and edit the include and exclude lists of directories and subdirectories, as necessary.

If the index resides on a drive or server volume separate from any part of the collection it applies to, moving either the collection or the index breaks the index. If you intend to move a document collection either to another network location or onto a CD, create and build the index in the same location as the collection.