feat: add comprehensive PDF support

- Add jsPDF for PDF generation from text/Markdown/HTML
- Add PDF.js for PDF text extraction (read PDFs)
- Support PDF → Text/Markdown conversions
- Support Markdown/HTML/Text → PDF conversions
- Implement page-by-page PDF text extraction
- Automatic pagination and formatting for generated PDFs

Supported PDF operations:
- Extract text from PDF files (all pages)
- Convert PDF to Markdown or plain text
- Create formatted PDFs from Markdown, HTML, or plain text
- Automatic text wrapping and page breaks

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/converters/pandocService.ts

@@ -1,6 +1,13 @@
 import { marked } from 'marked';
 import TurndownService from 'turndown';
 import type { ConversionOptions, ProgressCallback, ConversionResult } from '@/types/conversion';
+import {
+  pdfToText,
+  pdfToMarkdown,
+  markdownToPDF,
+  htmlToPDF,
+  plainTextToPDF,
+} from './pdfService';
 
 // Import DOMPurify only on client side
 let DOMPurify: any;
@@ -34,6 +41,31 @@ export async function convertWithPandoc(
 
     if (onProgress) onProgress(50);
 
+    // Handle PDF conversions
+    if (inputExt === 'pdf') {
+      // PDF input
+      if (outputFormat === 'txt') {
+        return await pdfToText(file, onProgress);
+      } else if (outputFormat === 'md' || outputFormat === 'markdown') {
+        return await pdfToMarkdown(file, onProgress);
+      } else {
+        throw new Error(`Conversion from PDF to ${outputFormat} not supported`);
+      }
+    }
+
+    // Handle conversions TO PDF
+    if (outputFormat === 'pdf') {
+      if (inputExt === 'md' || inputExt === 'markdown') {
+        return await markdownToPDF(file, onProgress);
+      } else if (inputExt === 'html' || inputExt === 'htm') {
+        return await htmlToPDF(file, onProgress);
+      } else if (inputExt === 'txt') {
+        return await plainTextToPDF(file, onProgress);
+      } else {
+        throw new Error(`Conversion from ${inputExt} to PDF not supported`);
+      }
+    }
+
     // Perform conversion based on input and output formats
     if (inputExt === 'md' || inputExt === 'markdown') {
       // Markdown input