[tools-and-trick] Add conversion from JPG to PDF

Author: jgbarah

tools-and-tricks.md

@@ -48,7 +48,7 @@ The last option for the 's_server' web server means "export all files in this di
 
 The first line can also be substituted by valid certificates. For example, certificates generated by Let´s Encrypt, via https://zerossl.com/
 
-# Image manipulation
+## Image manipulation
 
 Manipulating images is easy with convert, a tool that comes with ImageMagick:
 
@@ -82,4 +82,11 @@ convert img.jpg -rotate 90 img.jpg
 convert img.jpg -charcoal 3 img.jpg 
 ```
 
-[More details on convert](https://imagemagick.org/script/convert.php).
+[More details on convert](https://imagemagick.org/script/convert.php).
+
+
+## Convert JPG to PDF
+
+```
+img2pdf *.jpg --imgsize A4 --pagesize A4 --output doc.pdf
+```