diff --git a/Makefile.am b/Makefile.am
index 2ad04de..7819b95 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,6 +1,10 @@
 ACLOCAL_AMFLAGS		= -I m4
 
+if ENABLE_DOC
+SUBDIRS				= src doc
+else
 SUBDIRS				= src
+endif
 
 pkgincludedir		= $(includedir)/$(PACKAGE_NAME)
 pkginclude_HEADERS	= \
diff --git a/configure.ac b/configure.ac
index 8b2d5f8..6c8770b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -27,9 +27,25 @@ STRICT_CFLAGS="-Wall -Wextra -Werror -pipe -Wpedantic -Wconversion -Wshadow -Wvl
 AC_SUBST([STRICT_CFLAGS])
 
 
+# --enable-doc
+AC_ARG_ENABLE(
+			  [doc],
+			  [AS_HELP_STRING([--enable-doc], [Build PDF documentation with pdflatex (default: no)])],
+			  [enable_doc=$enableval],
+			  [enable_doc=no]
+			  )
+
+AS_IF([test "x$enable_doc" = "xyes"], [
+	AC_CHECK_PROG([PDFLATEX], [pdflatex], [pdflatex])
+	AS_IF([test -z "$PDFLATEX"],
+		  [AC_MSG_ERROR([--enable-doc requires pdflatex but it was not found])])
+])
+AM_CONDITIONAL([ENABLE_DOC], [test "x$enable_doc" = "xyes"])
+
 AC_CONFIG_FILES([
 				 Makefile
 				 src/Makefile
+				 doc/Makefile
 				 libft_ssl.pc
 				 ])
 
@@ -43,4 +59,5 @@ AC_MSG_NOTICE([
   CC     : $CC
   CFLAGS : $STRICT_CFLAGS $CFLAGS
   debug  : $enable_debug
+  doc    : $enable_doc
 ])
diff --git a/doc/Makefile.am b/doc/Makefile.am
new file mode 100644
index 0000000..a7d5447
--- /dev/null
+++ b/doc/Makefile.am
@@ -0,0 +1,12 @@
+EXTRA_DIST = libft_ssl.tex
+
+if ENABLE_DOC
+pdf: libft_ssl.pdf
+
+libft_ssl.pdf: libft_ssl.tex
+	$(PDFLATEX) $<
+	$(PDFLATEX) $<
+endif
+
+clean-local:
+	rm -f *.aux *.log *.toc *.out *.pdf
diff --git a/doc/libft_ssl.tex b/doc/libft_ssl.tex
new file mode 100644
index 0000000..95a3e0a
--- /dev/null
+++ b/doc/libft_ssl.tex
@@ -0,0 +1,56 @@
+\documentclass[a4paper,12pt]{article}
+
+\usepackage[utf8]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage{amsmath}
+\usepackage{amssymb}
+\usepackage{listings}
+\usepackage{xcolor}
+\usepackage{hyperref}
+\usepackage{geometry}
+
+\geometry{margin=2.5cm}
+
+\title{\textbf{libft\_ssl} \\ \large Cryptographic Hash Functions}
+\author{lohhiiccc}
+\date{}
+
+\begin{document}
+
+\maketitle
+\tableofcontents
+\newpage
+
+\section{Introduction}
+
+\texttt{libft\_ssl} is a C library implementing cryptographic hash functions
+from scratch. A cryptographic hash function maps an arbitrary-length input to a
+fixed-size digest. This operation is deterministic and one-way: it is
+computationally infeasible to recover the original input from its digest.
+
+The library currently implements the following algorithms:
+
+\begin{itemize}
+    \item \textbf{MD5} - produces a 128-bit digest.
+    \item \textbf{SHA-256} - produces a 256-bit digest.
+    \item \textbf{Whirlpool} - produces a 512-bit digest.
+\end{itemize}
+
+These functions are commonly used for data integrity verification, digital
+signatures, and message authentication codes (MACs).
+\newpage
+
+\section{Library core}
+
+\newpage
+
+\section{MD5}
+
+\newpage
+
+\section{SHA-256}
+
+\newpage
+
+\section{Whirlpool}
+\end{document}