Added book ads under PDF articles

Author: peterdevpl

_posts/2019-01-11-picking-a-php-tool-to-generate-pdfs.markdown

@@ -124,3 +124,5 @@ Please also remember that many tools are developed by the Open Source community
 
 * [Picking a PHP tool to read and manipulate PDF files]({% post_url 2019-01-25-picking-a-php-tool-to-read-and-manipulate-pdf-files %})
 * [PHP: How to take a screenshot of a PDF page]({% post_url 2021-01-28-php-how-to-take-a-screenshot-of-a-pdf-page %})
+
+{% include book.html %}

_posts/2019-01-25-picking-a-php-tool-to-read-and-manipulate-pdf-files.markdown

@@ -95,3 +95,5 @@ Check out the [List of PDF software](https://en.wikipedia.org/wiki/List_of_PDF_s
 
 * [Picking a PHP tool to generate PDFs (2021 update)]({% post_url 2019-01-11-picking-a-php-tool-to-generate-pdfs %})
 * [PHP: How to take a screenshot of a PDF page]({% post_url 2021-01-28-php-how-to-take-a-screenshot-of-a-pdf-page %})
+
+{% include book.html %}

_posts/2019-09-06-is-portable-document-format-obsolete.markdown

@@ -36,3 +36,5 @@ In Poland, we have electronic train tickets that can be downloaded on a smartpho
 ## Further reading
 
 [Will PDF files become obsolete in 5-10 years?](https://www.quora.com/Will-PDF-files-become-obsolete-in-5%E2%80%9310-years)
+
+{% include book.html %}

_posts/2021-01-28-php-how-to-take-a-screenshot-of-a-pdf-page.markdown

@@ -177,3 +177,5 @@ Check out [this StackOverflow thread to see more ideas on how to convert a PDF f
 
 * [Picking a PHP tool to generate PDFs (2021 update)]({% post_url 2019-01-11-picking-a-php-tool-to-generate-pdfs %})
 * [Picking a PHP tool to read and manipulate PDF files]({% post_url 2019-01-25-picking-a-php-tool-to-read-and-manipulate-pdf-files %})
+
+{% include book.html %}

_posts/2021-06-16-php-how-to-encrypt-a-pdf-document.markdown

@@ -111,3 +111,5 @@ To use AES, you need to pick a commercial tool, for example [Coherent PDF.](http
 ## Summary
 
 Document encryption is a good way to protect the document contents from being accessed by an unauthorized person. Banking documents are often sent via email and they could be stolen from a person's account. With strong encryption, it's not possible to read them.
+
+{% include book.html %}

_posts/2021-07-17-how-to-set-a-font-in-pdf.markdown

@@ -244,3 +244,5 @@ The mysterious number 32 which appears both in the command line call and the `ad
 | 131,072              | small caps                      |
 
 > TCPDF does not support OpenType nor WOFF2 fonts.
+
+{% include book.html %}

_sass/figures.scss

@@ -49,5 +49,13 @@ figcaption {
   figcaption {
     color: $text-color;
     font-size: 16px;
+
+    h2 {
+      font-size: 1.5em;
+    }
+
+    h3 {
+      font-size: 1.17em;
+    }
   }
 }