Fix: Improve PDF MIME type detection for uploads

- Added support for multiple PDF MIME types (application/x-pdf, etc.)
- Added fallback to file extension validation (.pdf)
- Added detailed logging for debugging upload issues
- Resolves 'Only PDF files are allowed' error for valid PDFs

backend/src/routes/documents.ts

@@ -32,11 +32,31 @@ const upload = multer({
     fileSize: parseInt(process.env['MAX_FILE_SIZE'] || '262144000'), // 250MB default
   },
   fileFilter: (req, file, cb) => {
-    // Only allow PDF files
-    if (file.mimetype === 'application/pdf') {
+    // Allow PDF files with multiple possible MIME types
+    const allowedMimeTypes = [
+      'application/pdf',
+      'application/x-pdf',
+      'application/acrobat',
+      'applications/vnd.pdf',
+      'text/pdf',
+      'text/x-pdf'
+    ];
+    
+    // Check MIME type or file extension
+    const isValidPDF = allowedMimeTypes.includes(file.mimetype) || 
+                       file.originalname.toLowerCase().endsWith('.pdf');
+    
+    // Log for debugging
+    console.log('Upload attempt:', {
+      mimetype: file.mimetype,
+      filename: file.originalname,
+      isValid: isValidPDF
+    });
+    
+    if (isValidPDF) {
       cb(null, true);
     } else {
-      cb(new Error('Only PDF files are allowed'));
+      cb(new Error(`Only PDF files are allowed. Received: ${file.mimetype} for file: ${file.originalname}`));
     }
   },
 });