Fix PDF download by returning file path instead of BytesIO object

app.py

@@ -5,6 +5,8 @@ from fuzzywuzzy import process
 from rdkit import Chem
 from rdkit.Chem import AllChem, Draw
 import io
+import tempfile
+import os
 from reportlab.pdfgen import canvas
 from reportlab.lib.pagesizes import letter
 from reportlab.lib.styles import getSampleStyleSheet
@@ -48,8 +50,11 @@ def generate_reaction_svg(name):
     return "Reaction not found."
 
 def generate_all_reactions_pdf():
-    pdf_output = io.BytesIO()
-    doc = SimpleDocTemplate(pdf_output, pagesize=letter)
+    # Create temporary file
+    temp_file = tempfile.NamedTemporaryFile(delete=False, suffix='.pdf')
+    temp_file.close()
+    
+    doc = SimpleDocTemplate(temp_file.name, pagesize=letter)
     styles = getSampleStyleSheet()
     story = []
     
@@ -84,8 +89,7 @@ def generate_all_reactions_pdf():
         story.append(Spacer(1, 12))
     
     doc.build(story)
-    pdf_output.seek(0)
-    return pdf_output
+    return temp_file.name
 
 def search_by_reaction_name(query):
     if not query: