diff --git a/src/poppler/document.py b/src/poppler/document.py
index 0872e5d..ee484bd 100644
--- a/src/poppler/document.py
+++ b/src/poppler/document.py
@@ -28,6 +28,7 @@
 from collections import namedtuple
 from functools import singledispatch, wraps
 from pathlib import Path
+from typing import Union, List
 
 
 PDFId = namedtuple("PDFId", ["permanent_id", "update_id"])
@@ -58,24 +59,24 @@ def __init__(self, poppler_document, data=None):
             raise ValueError("Corrupted or invalid PDF document")
 
         self._document = poppler_document
-        self._data = data
+        self._data = data  # just to prevent data from being GC'ed
 
     @ensure_unlocked
-    def create_font_iterator(self, page=0):
+    def create_font_iterator(self, page: int = 0) -> FontIterator:
         return FontIterator(self._document.create_font_iterator(page))
 
     @ensure_unlocked
-    def create_toc(self):
+    def create_toc(self) -> Union[Toc, None]:
         t = self._document.create_toc()
         return Toc(t) if t else None
 
     @ensure_unlocked
-    def create_page(self, index):
+    def create_page(self, index: int) -> Page:
         return Page(self._document.create_page(index))
 
     @property
     @ensure_unlocked
-    def author(self):
+    def author(self) -> str:
         return self.info_key("Author")
 
     @author.setter
@@ -167,7 +168,7 @@ def subject(self, subject):
 
     @property
     @ensure_unlocked
-    def title(self):
+    def title(self) -> str:
         return self.info_key("Title")
 
     @title.setter
@@ -178,7 +179,7 @@ def title(self, title):
 
     @property
     @ensure_unlocked
-    def pages(self):
+    def pages(self) -> int:
         return self._document.pages()
 
     @since(0, 74)
@@ -190,7 +191,7 @@ def create_destination_map(self):
         }
 
     @ensure_unlocked
-    def embedded_files(self):
+    def embedded_files(self) -> List[EmbeddedFile]:
         return [EmbeddedFile(f) for f in self._document.embedded_files()]
 
     @ensure_unlocked
@@ -198,10 +199,10 @@ def fonts(self):
         return [FontInfo(i) for i in self._document.fonts()]
 
     @ensure_unlocked
-    def has_embedded_files(self):
+    def has_embedded_files(self) -> bool:
         return self._document.has_embedded_files()
 
-    def has_permission(self, which):
+    def has_permission(self, which) -> bool:
         return self._document.has_permission(which)
 
     @ensure_unlocked
@@ -215,7 +216,7 @@ def set_info_date(self, key, val):
         return self._document.set_info_date(key, to_time_type(val))
 
     @ensure_unlocked
-    def info_key(self, key):
+    def info_key(self, key) -> str:
         info = self._document.info_key(key)
         return str(info)
 
@@ -239,13 +240,13 @@ def set_info_key(self, key, val):
     def info_keys(self):
         return self._document.info_keys()
 
-    def is_encrypted(self):
+    def is_encrypted(self) -> bool:
         return self._document.is_encrypted()
 
-    def is_linearized(self):
+    def is_linearized(self) -> bool:
         return self._document.is_linearized()
 
-    def is_locked(self):
+    def is_locked(self) -> bool:
         return self._document.is_locked()
 
     @property
@@ -277,18 +278,20 @@ def unlock(self, owner_password, user_password):
         return self._document.unlock(owner_password, user_password)
 
 
-def load_from_file(file_name, owner_password=None, user_password=None):
+def load_from_file(
+    file_name: Union[str, Path], owner_password: Union[str, None] = None, user_password: Union[str, None] = None
+) -> Document:
     return Document(
-        document.load_from_file(
-            str(file_name), owner_password or "", user_password or ""
-        )
+        document.load_from_file(file_name, owner_password, user_password)
     )
 
 
-def load_from_data(file_data: bytes, owner_password=None, user_password=None):
+def load_from_data(
+    file_data: bytes, owner_password: Union[str, None] = None, user_password: Union[str, None] = ""
+) -> Document:
     return Document(
-        document.load_from_data(file_data, owner_password or "", user_password or ""),
-        file_data
+        document.load_from_data(file_data, owner_password, user_password),
+        file_data,
     )
 
 
diff --git a/src/poppler/image.py b/src/poppler/image.py
index a8c27e2..df715a1 100644
--- a/src/poppler/image.py
+++ b/src/poppler/image.py
@@ -18,6 +18,8 @@
 from poppler.cpp import image
 from poppler.rectangle import Rectangle
 
+from typing import List
+
 
 class Image:
 
@@ -40,11 +42,11 @@ def from_object(cls, poppler_object):
         return cls(poppler_object=poppler_object)
 
     @property
-    def bytes_per_row(self):
+    def bytes_per_row(self) -> int:
         return self._image.bytes_per_row()
 
     @property
-    def const_data(self):
+    def const_data(self) -> bytes:
         return self._image.data()
 
     def copy(self, rect=None):
@@ -52,7 +54,7 @@ def copy(self, rect=None):
         return Image.from_object(image)
 
     @property
-    def data(self):
+    def data(self) -> bytes:
         return self._image.data()
 
     @data.setter
@@ -64,23 +66,23 @@ def format(self):
         return self._image.format()
 
     @property
-    def height(self):
+    def height(self) -> int:
         return self._image.height()
 
     @property
-    def is_valid(self):
+    def is_valid(self) -> bool:
         return self._image.is_valid()
 
-    def save(self, file_name, out_format, dpi=-1):
+    def save(self, file_name, out_format, dpi=-1) -> None:
         return self._image.save(str(file_name), out_format, dpi)
 
     @property
-    def width(self):
+    def width(self) -> int:
         return self._image.width()
 
     def memoryview(self):
         return memoryview(self._image)
 
     @staticmethod
-    def supported_image_formats():
+    def supported_image_formats() -> List[str]:
         return image.supported_image_formats()