Uploading a PDF to WordPress does not automatically make the words inside it searchable. You need a search plugin that extracts readable PDF text, adds that text to its index, and then returns either the PDF attachment or the page that contains it. Relevanssi Premium and SearchWP document this workflow, but neither can search text that exists only as an unprocessed image; SearchWP also cannot read encrypted PDFs.
What you need before indexing PDFs
- Files in an indexable location: Relevanssi’s documented PDF workflow uses WordPress attachment posts. SearchWP requires files to be Media Library entries with WordPress object IDs; documents kept only in an external document-management system are not supported through its documented route.
- Extractable text: Open representative files in a PDF reader and try to select and copy words. Image-only scans require OCR or another text source before a search index can match them. Encrypted PDFs cannot be read by SearchWP.
- A result destination: Decide whether a match should open the PDF itself or a parent post or page that provides context, access controls and navigation.
- Capacity and privacy approval: PDF extraction can enlarge the database and may involve external processing, depending on the plugin.
Choose an indexing plugin
| Decision | Relevanssi Premium | SearchWP |
|---|---|---|
| PDF availability | PDF and attachment indexing is a Premium feature, not part of the free plugin. | Its documented indexing system extracts supported document text. |
| Required storage | PDFs must be WordPress attachment posts for the documented workflow. | Files must be in the Media Library and have WordPress object IDs. |
| Result target | Return the attachment, or associate extracted content with its parent post. | The Engine and results template determine how matches are presented; programmatic searches require a form and results template. |
| Text limitations | Selectable text is readable; un-OCRed image text is not. The indexing service has a 256 MB hard file-size limit. | Unhighlightable image text and encrypted PDFs cannot be read. The cited documentation states no numeric file-size limit. |
| Relevance controls | Can index attachment content for the attachment or parent post; custom-field excerpts are available but may slow searches. | Engine settings choose sources and assign relevance weights, including a weight for document content. |
| Processing and capacity | Relevanssi documentation describes external PDF processing and warns that indexing can use substantial database space. | The cited documentation describes background indexing and delta updates for changed content. |
These are documented capabilities, not an independent performance comparison. Test each choice with your theme, permissions, representative files and expected queries.
Configure PDF indexing step by step
1. Inventory files and the visitor journey
List where PDFs live, which ones must be searchable and what a visitor should open after a match. If a PDF is attached to a product, policy page or course lesson, associating its text with that parent may be more useful than sending visitors directly to a bare file. For a download library, returning the attachment may be the clearer choice.
2. Set up Relevanssi Premium
- Install and activate Relevanssi Premium and enter the Premium API key; the vendor identifies PDF indexing as a Premium capability.
- Use the attachment controls to read PDF content. Relevanssi extracts and stores the text in the
_relevanssi_pdf_contentfield. - Choose whether that extracted content is indexed for the attachment post or for its parent post. Include the relevant post type in the indexing settings.
- For a large library, run the bulk PDF-reading control. Processing unread files can take time, so allow the operation to finish before judging search results.
- Inspect the extracted text or any reported error for several files before rebuilding or testing the complete index.
3. Set up SearchWP
- Confirm every document is an item in the WordPress Media Library with a WordPress object ID.
- Open the SearchWP Engine used by your site and include Media or the document source as appropriate.
- Enable document content as an indexed attribute and assign it a relevance weight alongside titles, excerpts and other fields.
- Run the initial index. SearchWP performs this in the background and applies smaller delta updates when indexed content changes.
- Check the front-end integration. Native search works code-free in many configurations; a custom or programmatic search needs a form and a results template.
Verify extraction before troubleshooting relevance
Test at least one normal text PDF, one long document and one scan. Select a distinctive phrase in a PDF reader, then search that exact phrase on the site. If the phrase cannot be selected, indexing cannot discover it until OCR or a supplied text field is added. With SearchWP, also check whether the file is encrypted.
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- If the plugin reports an extraction error, inspect the file and the attachment record before changing relevance weights.
- If extracted text is present but no result appears, confirm the attachment or parent post type is included in the index and rebuild the index after changing settings.
- If results point to the wrong place, change the attachment-versus-parent indexing choice (Relevanssi) or adjust the Engine and results template (SearchWP).
- If a phrase matches but the snippet is poor, review excerpt settings. Relevanssi notes that generating excerpts is the slowest part of searching and that very long PDF content can slow searches.
Tune the search experience
Choose what opens
Use attachment results when the PDF is the primary record users need to download. Associate content with the parent page when visitors need surrounding metadata, an explanation or a controlled access route.
Weight document text deliberately
PDF body text can overwhelm short page titles if it is weighted too heavily. Start with a modest document-content weight, then test distinctive terms from titles, headings and body text. Relevanssi supports phrase searches when visitors put a phrase in quotation marks; SearchWP exposes document-content weighting in the Engine.
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Test real queries
Create a small test set containing a unique name, a common word, a quoted phrase, a term found only in a PDF and a term found in both a page and a PDF. Record which result should rank first and repeat the set after each configuration change. The available documentation does not establish an independent speed or accuracy benchmark.
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File size and database growth
Relevanssi documents a 256 MB hard limit for its external PDF indexing service. This is a service limit for that indexer, not a general WordPress limit. The WordPress.org listing also warns that Relevanssi may require substantial database space, estimating a reasonable overall amount at about three times the size of the wp_posts table; that estimate is not a PDF-specific measurement. The cited SearchWP FAQ gives no comparable numeric file-size cap.
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External processing
Relevanssi states: “To read PDF contents, files are sent to an external Apache Tika server (hosted by UpCloud in the US or Germany).” It says the working copy is deleted immediately after processing and advises against sending highly confidential files. Obtain approval for that data flow and check current vendor terms, contracts and regional obligations before indexing sensitive documents. The cited SearchWP pages do not establish comparable processing-location details, so verify its current terms for your deployment.
Access control
Indexing a PDF does not automatically make its download public, but search snippets can reveal text if your results template exposes them. Test logged-out and logged-in searches, membership restrictions and direct attachment URLs. Exclude confidential files or fields when the plugin and site permissions require it.
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Launch checklist
- Every target file is a Media Library attachment or otherwise meets the selected plugin’s documented storage requirement.
- Text can be selected, or OCR has supplied text for scanned pages.
- Encrypted PDFs have been identified and excluded or replaced when using SearchWP.
- The correct attachment or parent-post result mode is configured.
- The index has completed, including any bulk PDF-reading step.
- Searches cover unique terms, quoted phrases, common terms and files of different lengths.
- Logged-out and restricted-user behavior has been checked.
- Database growth, extraction time and external data handling are acceptable for the site.
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