Update generate-pdf-files.md to include PDF/A support details and recommendations

Author: lyzhang0113

_articles/faq/generate-pdf-files.md

@@ -7,11 +7,66 @@ keywords: Dynamic Web TWAIN, Addon, separate, license
 breadcrumbText: How can I generate PDF/A files?
 description: How can I generate PDF/A files?
 date: 2021-12-01 01:09:41 +0800
-last_modified: 2022-07-08 02:17:16 +0800
+last_modified: 2025-12-10 15:15:15 +0800
 ---
 
 # Addon
 
 ## How can I generate PDF/A files?
 
-Dynamic Web TWAIN does not support the generation of PDF/A files.
+Dynamic Web TWAIN supports exporting documents as **PDF/A** starting from version **19.3**.
+PDF/A is an archival format designed for long-term preservation. The following variants are supported:
+
+### Supported PDF/A Versions
+
+| PDF/A Variant |    Underlying PDF Version   |
+|:-------------:|-----------------------------|
+| `pdf/a-1b`    | **1.4** (default)           |
+| `pdf/a-2b`    | **1.5** (default), 1.6, 1.7 |
+
+### What’s the difference between PDF/A-1b and PDF/A-2b?
+Although both variants ensure that documents can be reliably displayed in the future, they differ in terms of supported PDF features and compression options.
+- PDF/A-1b
+  - Uses the older PDF 1.4 specification.
+  - **Does not support JPEG2000** or JBIG2 image compression.
+  - Does not allow transparency.
+  - May result in larger file sizes and more conversion restrictions.
+
+- PDF/A-2b
+  - Based on newer PDF versions (1.5–1.7).
+  - Supports **JPEG2000**, JBIG2, transparency, and other modern PDF features.
+  - Typically requires **fewer changes** to the source document.
+  - Usually produces **smaller output** files.
+
+**Recommendation:**
+For most use cases, we recommend using **`pdf/a-2b`**.
+It offers better compression support, fewer limitations, and higher compatibility with modern PDFs while still meeting archival requirements.
+
+### Behavior and Defaults
+
+- If you do not set `pdfaVersion`, the export uses standard PDF format (non-PDF/A).
+
+- If you set `pdfaVersion` but forget to set `version`, or set a mismatched or incorrect PDF version, Dynamic Web TWAIN automatically falls back to a default PDF version:
+  - `pdf/a-1b` → defaults to PDF `1.4`
+  - `pdf/a-2b` → defaults to PDF `1.5`
+
+### How to Export as PDF/A
+
+Configure PDF output using [`Write.Setup()`](/_articles/info/api/Addon_PDF.html#writesetup) before calling any save function.
+
+```javascript
+DWTObject.Addon.PDF.Write.Setup({
+    version: "1.5",          // [optional] 1.4 for "pdf/a-1b"; 1.5/1.6/1.7 for "pdf/a-2b"
+    pdfaVersion: "pdf/a-2b"  // "pdf/a-1b" or "pdf/a-2b"
+});
+```
+
+After configuring `pdfaVersion`, all APIs that output PDF files will automatically generate PDF/A-compliant PDFs. This includes, but is not limited to:
+
+- **Save APIs** like: [`SaveAsPDF()`](/_articles/info/api/WebTwain_IO.html#saveaspdf), [`SaveSelectedImagesAsMultiPagePDF()`](/_articles/info/api/WebTwain_IO.html#saveselectedimagesasmultipagepdf), [`SaveAllAsPDF()`](/_articles/info/api/WebTwain_IO.html#saveallaspdf)
+
+- **Conversion APIs** like: [`ConvertToBlob()`](/_articles/info/api/WebTwain_IO.html#converttoblob), [`ConvertToBase64()`](/_articles/info/api/WebTwain_IO.html#converttobase64)
+
+- **Upload APIs** like: [`HTTPUpload()`](/_articles/info/api/WebTwain_IO.html#httpupload), [`FTPUpload()`](/_articles/info/api/WebTwain_IO.html#ftpupload), [`httpUploadBlob()`](/_articles/info/api/WebTwain_IO.html#httpuploadblob)
+
+- **OCR Output APIs** like: [`SaveToPath()`](/_articles/info/api/Addon_OCR.html#savetopath), [`SaveAsBase64()`](/_articles/info/api/Addon_OCR.html#saveasbase64), [`SaveAsBlob()`](/_articles/info/api/Addon_OCR.html#saveasblob)