diff --git a/src/shop/pdf.py b/src/shop/pdf.py
index ebad4b6d..32cafc92 100644
--- a/src/shop/pdf.py
+++ b/src/shop/pdf.py
@@ -3,7 +3,9 @@ from wkhtmltopdf.views import PDFTemplateResponse
 from PyPDF2 import PdfFileWriter, PdfFileReader
 from django.test.client import RequestFactory
 from django.conf import settings
-import io, logging
+import logging
+import io
+import os
 logger = logging.getLogger("bornhack.%s" % __name__)
 
 
@@ -13,10 +15,10 @@ def generate_pdf_letter(filename, template, formatdict):
     request.user = AnonymousUser()
     request.session = {}
 
-    ### produce text-only PDF from template
+    # produce text-only PDF from template
     pdfgenerator = PDFTemplateResponse(
         request=request,
-        template=template, 
+        template=template,
         context=formatdict,
         cmd_options={
             'margin-top': 50,
@@ -26,33 +28,35 @@ def generate_pdf_letter(filename, template, formatdict):
     textonlypdf = io.BytesIO()
     textonlypdf.write(pdfgenerator.rendered_content)
 
-    ### create a blank pdf to work with
+    # create a blank pdf to work with
     finalpdf = PdfFileWriter()
 
-    ### open the text-only pdf
+    # open the text-only pdf
     pdfreader = PdfFileReader(textonlypdf)
 
-    ### get watermark from watermark file
-    watermark = PdfFileReader(open("%s/pdf/%s" % (settings.STATICFILES_DIRS[0], settings.PDF_LETTERHEAD_FILENAME), 'rb'))
+    # get watermark from watermark file
+    watermark = PdfFileReader(
+        open(os.path.join(settings.STATICFILES_DIRS[0], 'pdf', settings.PDF_LETTERHEAD_FILENAME), 'rb')
+    )
 
-    ### add the watermark to all pages
+    # add the watermark to all pages
     for pagenum in range(pdfreader.getNumPages()):
         page = watermark.getPage(0)
         try:
             page.mergePage(pdfreader.getPage(pagenum))
         except ValueError:
-            ### watermark pdf might be broken?
+            # watermark pdf might be broken?
             return False
-        ### add page to output
+        # add page to output
         finalpdf.addPage(page)
 
-    ### save the generated pdf to the archive
-    fullpath = settings.PDF_ARCHIVE_PATH+filename
+    # save the generated pdf to the archive
+    fullpath = os.path.join(settings.PDF_ARCHIVE_PATH, filename)
     with open(fullpath, 'wb') as fh:
         finalpdf.write(fh)
         logger.info('Saved pdf to archive: %s' % fullpath)
 
-    ### return a file object with the data
+    # return a file object with the data
     returnfile = io.BytesIO()
     finalpdf.write(returnfile)
     return returnfile