There are many PDF/A validation and conversion tools available, both for desktop users and developers.
We’ve put together a list of tools for comparison:

User/Desktop tools:

 Tool  Price  Notes
 PDF Studio Pro  $139  PDF editor with validation/conversion
 Adobe Acrobat  $449  PDF editor with validation/conversion (?)
 Bluebeam Revu  $349  PDF editor with validation/conversion
 Callas pdfaPilot  $496  Acrobat plug-in / standalone converter
 Enfocus Pitstop Pro  $906  Acrobat plug-in
 Luratech PDF Compressor  ~$70  PDF/A conversion only

Developer/SDK tools:

 Tool  Price  Notes
 Qoppa PDF/A SDK jPDFPreflight  $1200  Convert/Validate
 activePDF Doc Convertor  $2,999  Convert
 activePDF Meridian  $5,500  Server-based PDF printer
 Aspose PDF for Java  $999 (one developer only)  Convert
 Callas pdfaPilot SDK  $5,000 or $9,000 depending on platform  Create/Convert
 PDFlib PLOP  $185  PDF/A metadata conversion
 PDFlib  $1175  Create/Convert
 PDF-Tools  PDF Validator SDK  $428  Validate
 PDF-Tools  PDF Security SDK  $570  Applies signature to PDF/A documents
 PDF-Tools PDF to PDF/A Converter SDK  $855  Convert