To validate a PDF before sending it, check the recipient’s rules first, then test the exact final file—not the Word document, design file, or earlier export. Open every page, run a structural check, test the text and interactive features you rely on, and use specialist validation for PDF/A, digital signatures, or accessibility when those requirements apply.
A general validator can find useful format and parsing problems, but no single green badge proves that a PDF is authentic, malware-free, accessible, standards-compliant, or acceptable to every portal. The reliable workflow is a short sequence of checks tied to the actual destination.
The 7-step PDF preflight
- 1. Freeze the final copy. Save it with a clear filename and stop editing that copy.
- 2. Read the recipient’s rules. Note size, filename, password, PDF/A, signature, form, and accessibility requirements.
- 3. Open and inspect every page. Use a second viewer if the document is important.
- 4. Run a general PDF validator. Check file identity, parseability, structure, and suspicious indicators.
- 5. Test the content. Select text, follow links, check fonts, and try required fields or attachments.
- 6. Run specialist checks. Validate the required PDF/A profile, signatures, or accessibility separately.
- 7. Send the file you tested. Do not print, optimize, flatten, or re-export it afterward without retesting.
Start With the Destination, Not the Tool
“Valid PDF” does not have one universal meaning. An email attachment, procurement portal, court filing system, print shop, archive, and accessible website can all impose different rules. Write down the decision you need before you upload the file anywhere.
| Destination requirement | Check to run | Question it answers |
|---|---|---|
| “Upload a readable PDF” | Open it, visually inspect it, then run a general validator | Does this exact file open, parse, and look complete? |
| “Submit PDF/A-2b” | A validator for the named PDF/A part and level | Does the file conform to that specific profile? |
| “Keep the digital signature valid” | Signature integrity, certificate, timestamp, and trust checks | Was the signed content changed, and is the trust chain acceptable? |
| “Publish an accessible PDF” | Automated accessibility checks plus manual review | Can people navigate, understand, and operate the document? |
| “No hidden or sensitive information” | Metadata, attachment, action, layer, and redaction review | Does the final copy expose information that should not leave your organization? |
1. Freeze the Exact File You Plan to Send
Export the PDF once, give it a deliberate filename, and make that file your test subject. Keep the editable source and an untouched copy separately. This prevents a common handoff mistake: validating one version, making a small last-minute change, and sending an untested export.
If the PDF is already digitally signed, preserve the original before doing anything else. Rewriting, optimizing, printing to PDF, or changing metadata can alter signed bytes. Use the workflow in How to verify PDF digital signatures before deciding whether any change is allowed.
2. Copy the Recipient’s Rules Into a Mini Checklist
Look for an upload limit, permitted filename characters, encryption restrictions, a required PDF version or PDF/A profile, embedded-font rules, signature requirements, form-field rules, and whether attachments, JavaScript, or other actions are prohibited. When a portal provides an error message, preserve the exact wording.
Do not “fix” the PDF generically before you know the failed rule. Compression may solve a size limit but reduce image quality. Flattening may improve viewer consistency but remove usable form fields. Re-exporting may repair structure but invalidate a signature. The destination determines the safe action.
3. Open and Inspect the Final PDF
- Open the saved PDF from disk. Do not rely on the export preview inside the source application.
- Review the first, last, and every high-risk page. Check page order, cropping, blank pages, charts, signatures, footnotes, and anything near a page edge.
- Try a second viewer for important documents. Different viewers can expose missing fonts, broken forms, or rendering assumptions.
- Search for a distinctive phrase. If text should be searchable but is not, the PDF may be image-only or have a damaged text layer. See how to search a scanned PDF.
4. Run a General Structural Check
Run the exact file through the PDF Validator. PDFCheck checks whether the upload identifies as a PDF and can be parsed, then surfaces document, security, font, metadata, and suspicious-content indicators for review.
This is diagnostic, not a universal certificate. A file can open in a forgiving viewer but still fail a recipient’s rules. It can also pass a general structural check and fail a named PDF/A profile, signature trust policy, accessibility requirement, or security scan. If you already have a rejection message, use the targeted steps in How to fix an invalid PDF error.
5. Test the Features the Reader Needs
A structurally readable PDF can still fail its job. Test the functions that matter in the destination workflow:
- Text: select, copy, and search a sentence. If you need machine-readable content, inspect it with the PDF Text Extractor.
- Fonts: review embedded-font indicators with the PDF Font Checker, especially for print, archive, or cross-device delivery.
- Links and navigation: open important links, bookmarks, and table-of-contents entries.
- Forms: enter sample text in a working copy, save, reopen, and confirm the value remains visible. Keep the untouched delivery copy separate.
- Metadata and attachments: inspect author, title, software, embedded files, actions, and other properties before external sharing. Remove metadata only from an authorized copy, then retest it.
6. Run the Specialist Check the Requirement Names
PDF/A
Use the exact part and conformance level requested by the recipient. The PDF/A Validator can screen likely blockers. For formal machine-verifiable conformance, use the recipient’s required validator or a purpose-built engine such as veraPDF.
Digital signatures
Check the untouched signed file with the PDF Signature Checker, then review certificate trust, revocation information, and timestamps according to the receiving organization’s policy.
Accessibility
Start with the PDF Accessibility Checker, then manually review reading order, headings, link purpose, form labels, keyboard use, language, and meaningful alternatives. Automated results alone do not establish conformance.
7. Protect Privacy, Then Send the Tested Copy
Confirm that comments, hidden layers, attachments, form values, filenames, and metadata are appropriate for the recipient. Visual black rectangles are not reliable redaction unless the underlying content has actually been removed. Use your organization’s approved redaction and malware-scanning process for sensitive or untrusted documents.
After any authorized removal, optimization, flattening, signing, or conversion, repeat the relevant checks. Then attach or upload that exact tested file. Do not substitute another copy with the same-looking filename.
When a Check Fails: Next Action
| What you see | Safe next action |
|---|---|
| The file will not open or parse | Retrieve the original again or re-export from the trusted source; do not keep converting a damaged copy. |
| It opens, but the portal rejects it | Match the exact error to the portal’s size, security, profile, filename, or feature rules. |
| Text looks right but cannot be searched | Check whether pages are scans; OCR an authorized working copy and proofread the output. |
| Fonts substitute or characters disappear | Return to the source file, resolve font licensing/embedding, export again, and compare visually. |
| A signature is invalid after editing | Return to the unsigned source, make the approved change, and restart the signature workflow. |
| A PDF/A or accessibility check fails | Fix the named rule in the source when possible, re-export, and rerun that same specialist check. |
What PDFCheck cannot certify
PDFCheck can surface observable file properties and diagnostic indicators. It cannot prove that visible claims are true, clear malware, establish legal authenticity, guarantee portal acceptance, replace a recipient-mandated conformance engine, or complete the human part of an accessibility audit.
If the file is still a link on a web page, first follow the Chrome before-download checking workflow to identify and inspect the exact PDF before saving it locally.
Authoritative References
Adobe’s Preflight profile documentation, updated February 26, 2026, explains how checks and fixups are grouped for PDF analysis, printing, PDF/A, PDF/E, and PDF/X workflows. Adobe’s Preflight report documentation describes inventories for resources such as fonts, images, metadata, and color spaces.
The veraPDF validation documentation lists supported PDF/A profiles and the machine-verifiable requirements it can test. For signed files, Adobe’s digital-signature validation guidance, updated November 5, 2025, covers signature status, certificates, and timestamps.
For accessibility, the W3C WCAG 2.2 techniques, updated May 11, 2026, include PDF-specific examples for text alternatives, reading order, OCR, headings, form labels, links, language, and page numbering. W3C notes that techniques are informative examples; conformance is determined against the applicable requirements.