diff --git a/.gitmodules b/.gitmodules
index fc49028..0e2fb5e 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,6 @@
 [submodule "app/libgocryptfs"]
 	path = app/libgocryptfs
 	url = https://forge.chapril.org/hardcoresushi/libgocryptfs.git
+[submodule "libpdfviewer"]
+	path = libpdfviewer
+	url = https://forge.chapril.org/hardcoresushi/libpdfviewer.git
diff --git a/README.md b/README.md
index 9d309d1..18eb756 100644
--- a/README.md
+++ b/README.md
@@ -101,14 +101,10 @@ You also need to install the Android SDK build tools and the [Android NDK](https
 
 #### Download Sources
 ```
-$ git clone https://github.com/hardcore-sushi/DroidFS.git
-```
-Download [libgocryptfs](https://forge.chapril.org/hardcoresushi/libgocryptfs):
-```
+$ git clone --recurse-submodules https://github.com/hardcore-sushi/DroidFS.git
 $ cd DroidFS
-$ git submodule update --init
 ```
-libgocryptfs needs OpenSSL:
+[libgocryptfs](https://forge.chapril.org/hardcoresushi/libgocryptfs) needs OpenSSL:
 ```
 $ cd app/libgocryptfs
 $ wget https://www.openssl.org/source/openssl-1.1.1m.tar.gz
diff --git a/app/build.gradle b/app/build.gradle
index 5dd9600..96e74bf 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -55,6 +55,7 @@ android {
 }
 
 dependencies {
+    implementation project(":libpdfviewer:app")
     implementation fileTree(dir: "libs", include: ["*.jar"])
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
     implementation 'androidx.core:core-ktx:1.7.0'
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 775016d..f820d2c 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -77,6 +77,9 @@
         <activity
             android:name=".file_viewers.VideoPlayer"
             android:configChanges="screenSize|orientation" />
+        <activity
+            android:name=".file_viewers.PdfViewer"
+            android:configChanges="screenSize|orientation" />
         <activity
             android:name=".file_viewers.AudioPlayer"
             android:configChanges="screenSize|orientation" />
diff --git a/app/src/main/java/sushi/hardcore/droidfs/ConstValues.kt b/app/src/main/java/sushi/hardcore/droidfs/ConstValues.kt
index 31c19d8..a1d2291 100644
--- a/app/src/main/java/sushi/hardcore/droidfs/ConstValues.kt
+++ b/app/src/main/java/sushi/hardcore/droidfs/ConstValues.kt
@@ -19,6 +19,7 @@ class ConstValues {
             Pair("image", listOf("png", "jpg", "jpeg", "gif", "webp", "bmp")),
             Pair("video", listOf("mp4", "webm", "mkv", "mov")),
             Pair("audio", listOf("mp3", "ogg", "m4a", "wav", "flac")),
+            Pair("pdf", listOf("pdf")),
             Pair("text", listOf("txt", "json", "conf", "log", "xml", "java", "kt", "py", "pl", "rb", "go", "c", "h", "cpp", "hpp", "rs", "sh", "bat", "js", "html", "css", "php", "yml", "yaml", "toml", "ini", "md", "properties"))
         )
 
@@ -35,6 +36,9 @@ class ConstValues {
         fun isAudio(path: String): Boolean {
             return isExtensionType("audio", path)
         }
+        fun isPDF(path: String): Boolean {
+            return isExtensionType("pdf", path)
+        }
         fun isText(path: String): Boolean {
             return isExtensionType("text", path)
         }
diff --git a/app/src/main/java/sushi/hardcore/droidfs/GocryptfsVolume.kt b/app/src/main/java/sushi/hardcore/droidfs/GocryptfsVolume.kt
index 4a1f0eb..2f310ad 100644
--- a/app/src/main/java/sushi/hardcore/droidfs/GocryptfsVolume.kt
+++ b/app/src/main/java/sushi/hardcore/droidfs/GocryptfsVolume.kt
@@ -238,8 +238,8 @@ class GocryptfsVolume(val applicationContext: Context, var sessionID: Int) {
         }
     }
 
-    fun loadWholeFile(fullPath: String, maxSize: Long? = null): Pair<ByteArray?, Int> {
-        val fileSize = getSize(fullPath)
+    fun loadWholeFile(fullPath: String, size: Long? = null, maxSize: Long? = null): Pair<ByteArray?, Int> {
+        val fileSize = size ?: getSize(fullPath)
         return if (fileSize >= 0) {
             maxSize?.let {
                 if (fileSize > it) {
diff --git a/app/src/main/java/sushi/hardcore/droidfs/adapters/ExplorerElementAdapter.kt b/app/src/main/java/sushi/hardcore/droidfs/adapters/ExplorerElementAdapter.kt
index ff2b15f..146668e 100644
--- a/app/src/main/java/sushi/hardcore/droidfs/adapters/ExplorerElementAdapter.kt
+++ b/app/src/main/java/sushi/hardcore/droidfs/adapters/ExplorerElementAdapter.kt
@@ -127,7 +127,7 @@ class ExplorerElementAdapter(
                 adapter.gocryptfsVolume?.let { volume ->
                     displayThumbnail = true
                     Thread {
-                        volume.loadWholeFile(fullPath, 50_000_000).first?.let {
+                        volume.loadWholeFile(fullPath, maxSize = 50_000_000).first?.let {
                             if (displayThumbnail) {
                                 adapter.activity.runOnUiThread {
                                     if (displayThumbnail) {
diff --git a/app/src/main/java/sushi/hardcore/droidfs/explorers/BaseExplorerActivity.kt b/app/src/main/java/sushi/hardcore/droidfs/explorers/BaseExplorerActivity.kt
index a2fd394..66cd168 100644
--- a/app/src/main/java/sushi/hardcore/droidfs/explorers/BaseExplorerActivity.kt
+++ b/app/src/main/java/sushi/hardcore/droidfs/explorers/BaseExplorerActivity.kt
@@ -25,6 +25,7 @@ import sushi.hardcore.droidfs.BaseActivity
 import sushi.hardcore.droidfs.ConstValues
 import sushi.hardcore.droidfs.ConstValues.Companion.isAudio
 import sushi.hardcore.droidfs.ConstValues.Companion.isImage
+import sushi.hardcore.droidfs.ConstValues.Companion.isPDF
 import sushi.hardcore.droidfs.ConstValues.Companion.isText
 import sushi.hardcore.droidfs.ConstValues.Companion.isVideo
 import sushi.hardcore.droidfs.GocryptfsVolume
@@ -35,10 +36,7 @@ import sushi.hardcore.droidfs.content_providers.ExternalProvider
 import sushi.hardcore.droidfs.content_providers.RestrictedFileProvider
 import sushi.hardcore.droidfs.file_operations.FileOperationService
 import sushi.hardcore.droidfs.file_operations.OperationFile
-import sushi.hardcore.droidfs.file_viewers.AudioPlayer
-import sushi.hardcore.droidfs.file_viewers.ImageViewer
-import sushi.hardcore.droidfs.file_viewers.TextEditor
-import sushi.hardcore.droidfs.file_viewers.VideoPlayer
+import sushi.hardcore.droidfs.file_viewers.*
 import sushi.hardcore.droidfs.util.PathUtils
 import sushi.hardcore.droidfs.widgets.CustomAlertDialogBuilder
 
@@ -164,6 +162,7 @@ open class BaseExplorerActivity : BaseActivity() {
                     "image" -> startFileViewer(ImageViewer::class.java, path)
                     "video" -> startFileViewer(VideoPlayer::class.java, path)
                     "audio" -> startFileViewer(AudioPlayer::class.java, path)
+                    "pdf" -> startFileViewer(PdfViewer::class.java, path)
                     "text" -> startFileViewer(TextEditor::class.java, path)
                     "external" -> if (usf_open) {
                         openWithExternalApp(path)
@@ -197,6 +196,9 @@ open class BaseExplorerActivity : BaseActivity() {
                     isText(fullPath) -> {
                         startFileViewer(TextEditor::class.java, fullPath)
                     }
+                    isPDF(fullPath) -> {
+                        startFileViewer(PdfViewer::class.java, fullPath)
+                    }
                     isAudio(fullPath) -> {
                         startFileViewer(AudioPlayer::class.java, fullPath)
                     }
diff --git a/app/src/main/java/sushi/hardcore/droidfs/file_viewers/FileViewerActivity.kt b/app/src/main/java/sushi/hardcore/droidfs/file_viewers/FileViewerActivity.kt
index 58ba635..e5dedda 100644
--- a/app/src/main/java/sushi/hardcore/droidfs/file_viewers/FileViewerActivity.kt
+++ b/app/src/main/java/sushi/hardcore/droidfs/file_viewers/FileViewerActivity.kt
@@ -66,8 +66,8 @@ abstract class FileViewerActivity: BaseActivity() {
         }
     }
 
-    protected fun loadWholeFile(path: String): ByteArray? {
-        val result = gocryptfsVolume.loadWholeFile(path)
+    protected fun loadWholeFile(path: String, fileSize: Long? = null): ByteArray? {
+        val result = gocryptfsVolume.loadWholeFile(path, size = fileSize)
         if (result.second != 0) {
             val dialog = CustomAlertDialogBuilder(this, themeValue)
                 .setTitle(R.string.error)
diff --git a/app/src/main/java/sushi/hardcore/droidfs/file_viewers/PdfViewer.kt b/app/src/main/java/sushi/hardcore/droidfs/file_viewers/PdfViewer.kt
new file mode 100644
index 0000000..02ba9d8
--- /dev/null
+++ b/app/src/main/java/sushi/hardcore/droidfs/file_viewers/PdfViewer.kt
@@ -0,0 +1,51 @@
+package sushi.hardcore.droidfs.file_viewers
+
+import android.view.Menu
+import android.view.MenuItem
+import android.widget.TextView
+import androidx.appcompat.widget.Toolbar
+import sushi.hardcore.droidfs.R
+import sushi.hardcore.droidfs.databinding.ActivityPdfViewerBinding
+import java.io.ByteArrayInputStream
+import java.io.File
+
+class PdfViewer: FileViewerActivity() {
+    private lateinit var binding: ActivityPdfViewerBinding
+
+    override fun hideSystemUi() {
+        //don't hide system ui
+    }
+
+    override fun getFileType(): String {
+        return "pdf"
+    }
+
+    override fun viewFile() {
+        binding = ActivityPdfViewerBinding.inflate(layoutInflater)
+        val toolbar = binding.root.findViewById<Toolbar>(R.id.toolbar)
+        setSupportActionBar(toolbar)
+        title = ""
+        val titleText = toolbar.findViewById<TextView>(R.id.title_text)
+        val fileName = File(filePath).name
+        titleText.text = fileName
+        binding.pdfViewer.activity = this
+        setContentView(binding.root)
+        val fileSize = gocryptfsVolume.getSize(filePath)
+        loadWholeFile(filePath, fileSize)?.let {
+            binding.pdfViewer.loadPdf(ByteArrayInputStream(it), fileName, fileSize)
+        }
+    }
+
+    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
+        binding.pdfViewer.onCreateOptionMenu(menu)
+        return super.onCreateOptionsMenu(menu)
+    }
+
+    override fun onPrepareOptionsMenu(menu: Menu?): Boolean {
+        return binding.pdfViewer.onPrepareOptionsMenu(menu)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return binding.pdfViewer.onOptionsItemSelected(item) || super.onOptionsItemSelected(item)
+    }
+}
diff --git a/app/src/main/res/layout/activity_pdf_viewer.xml b/app/src/main/res/layout/activity_pdf_viewer.xml
new file mode 100644
index 0000000..221bbda
--- /dev/null
+++ b/app/src/main/res/layout/activity_pdf_viewer.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <include android:id="@+id/toolbar" layout="@layout/toolbar"/>
+
+    <org.grapheneos.pdfviewer.PdfViewer
+        android:id="@+id/pdf_viewer"
+        android:layout_height="match_parent"
+        android:layout_width="match_parent"/>
+
+</LinearLayout>
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 9a41126..c56ef3c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,7 +6,7 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.0.4'
+        classpath 'com.android.tools.build:gradle:7.1.1'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
diff --git a/libpdfviewer b/libpdfviewer
new file mode 160000
index 0000000..4e4b7c5
--- /dev/null
+++ b/libpdfviewer
@@ -0,0 +1 @@
+Subproject commit 4e4b7c5da4dddbc3841abd450fa250936be70f4e
diff --git a/settings.gradle b/settings.gradle
index 78d2b97..ee71f79 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -1,2 +1,2 @@
-include ':app'
+include ':app', ':libpdfviewer:app'
 rootProject.name = "DroidFS"
\ No newline at end of file