什么是 PDF/A？—— PDF 归档格式详解

A regular PDF can reference external fonts, contain JavaScript, link to external content, and use encryption. These features make it flexible but potentially fragile — an external font might be unavailable, a linked resource might disappear, and encryption could become unreadable if the password is lost.

PDF/A eliminates all external dependencies:

- All fonts must be embedded in the file - JavaScript is not allowed - External content references are prohibited - Audio and video are not allowed (in PDF/A-1 and PDF/A-2) - Encryption is not allowed - Color profiles must be embedded

The result is a file that is guaranteed to look the same whether opened today or in 50 years.

**PDF/A-1 (ISO 19005-1:2005):** The original standard. Based on PDF 1.4. Two sub-levels: - PDF/A-1b (basic): Ensures visual appearance is preserved. - PDF/A-1a (accessible): Adds document structure tags for accessibility.

**PDF/A-2 (ISO 19005-2:2011):** Based on PDF 1.7. Adds support for JPEG2000 compression, transparency, and embedded PDF/A files (useful for archiving email attachments).

**PDF/A-3 (ISO 19005-3:2012):** Same as PDF/A-2 but allows embedding any file type (XML data, spreadsheets, CAD files) as attachments.

For most use cases, PDF/A-1b or PDF/A-2b is sufficient. PDF/A-1a is recommended when accessibility compliance is also required.

**Government agencies:** Many countries require PDF/A for official filings, tax documents, and public records. The U.S. National Archives, the EU e-invoicing standard, and Germany's TR-RESISCAN regulation all mandate or recommend PDF/A.

**Courts:** Federal courts in several jurisdictions require or prefer PDF/A for electronic case filings.

**Financial institutions:** Banks and insurance companies use PDF/A for contract archival and regulatory compliance.

**Healthcare:** Patient records and regulatory submissions often require long-term format preservation.

**Libraries and archives:** Digital preservation standards almost universally recommend PDF/A for scanned books, journals, and historical documents.

1. Open the WhiskFile PDF to PDF/A tool.

2. Upload the PDF you want to convert.

3. Select the compliance level (PDF/A-1b is the most common and widely accepted).

4. Click "Convert to PDF/A". The tool embeds all fonts, removes JavaScript, strips external references, and validates the result against the PDF/A specification.

5. Download the compliant PDF/A file.

If the source PDF contains elements that cannot be made PDF/A compliant (like embedded video), the tool will report which elements were removed or modified.

Open the PDF in a viewer that supports PDF/A detection (like Adobe Reader — it shows a blue bar saying "This file claims compliance with the PDF/A standard"). Alternatively, use the WhiskFile Edit PDF Metadata tool to inspect the document's metadata, which includes the PDF/A conformance level if present.

Note that a PDF "claiming" PDF/A compliance does not guarantee it is actually compliant. Validation tools check the file structure against the specification to confirm true compliance.