Try to open pdf files properly in EWW

README.org

@@ -829,6 +829,7 @@ defined in this Org file.
         (smart-latex-engrave-org-source-blocks :no-manual t)
         (toggle-engrave-faces-latex-face-apply-override :no-manual t)
         (toggle-engrave-faces-latex-face-mapper-override :no-manual t)
+        (toggle-eww-display-pdf-around :no-manual t)
         (toggle-org-babel-python-format-session-value-override :no-manual t)
         "Python"
         (choose-common-python-interpreter :no-manual t))))
@@ -4960,11 +4961,15 @@ Listing [[lst:configure-browse-url]] configures =browse-url=.
                                                nil t)))))
 #+end_src
 
-#+caption[Configure =eww= rendering]:
-#+caption: Configure =eww= rendering.
-#+name: lst:configure-eww-rendering
+#+caption[Rename =eww= buffers and display =pdf= links properly]:
+#+caption: Rename =eww= buffers and display =pdf= links properly.
+#+name: lst:rename-eww-buffer-display-pdf-links
 #+begin_src emacs-lisp
   (with-eval-after-load 'eww
+    (defun eww-display-pdf-as-binary (fn &rest args)
+      (let ((buffer-file-coding-system 'binary))
+        (apply fn args)))
+
     (defun eww-rename-buffer ()
       "Rename the buffer using title or url."
       (let* ((title (plist-get eww-data :title))
@@ -4972,6 +4977,14 @@ Listing [[lst:configure-browse-url]] configures =browse-url=.
         (rename-buffer (format "*%s # eww*" name) t)))
 
     (add-hook 'eww-after-render-hook #'eww-rename-buffer))
+
+  (with-eval-after-load 'emacs
+    (defun toggle-eww-display-pdf-around ()
+      "Toggle `eww-display-advice' advice."
+      (interactive)
+      (toggle-advice 'eww-display-pdf :around #'eww-display-pdf-as-binary))
+
+    (toggle-eww-display-pdf-around))
 #+end_src
 
 *** [[https://en.wikipedia.org/wiki/Media_type#Mailcap][Mailcap]]