Fix some comments

@@ -17,7 +17,7 @@
 part of pdf;
 
 class PdfFont extends PdfObject {
-  /// Thedf type of the font, usually /Type1
+  /// The df type of the font, usually /Type1
   final String subtype;
 
   /// Constructs a [PdfFont]. This will attempt to map the font from a known

@@ -173,7 +173,7 @@ class PdfGraphics {
   ///
   /// @param x coordinate
   /// @param y coordinate
-  /// @oaran s String to draw
+  /// @param s String to draw
   void drawString(PdfFont font, double size, String s, double x, double y) {
     if (!page.fonts.containsKey(font.name)) {
       page.fonts[font.name] = font;
@@ -558,7 +558,7 @@ class PdfGraphics {
   }
 
   /// This is used to add a polygon to the current path.
-  /// Used by drawPolygon(), drawPolyline() and fillPolygon() etal
+  /// Used by drawPolygon()
   ///
   /// @param p Array of coordinates
   /// @see #drawPolygon

@@ -39,7 +39,7 @@ class PdfImage extends PdfXObject {
 
   /// Creates a new [PdfImage] instance.
   ///
-  /// @param imgage an [Uint8List] value
+  /// @param image an [Uint8List] value
   /// @param width
   /// @param height
   /// @param alpha if the image is transparent

@@ -42,7 +42,7 @@ class PdfObject {
   }
 
   /// Writes the object to the output stream.
-  /// This method must be overidden.
+  /// This method must be overridden.
   ///
   /// Note: It should not write any other objects, even if they are
   /// it's Kids, as they will be written by the calling routine.

@@ -55,7 +55,7 @@ class PdfOutline extends PdfObject {
   /// This method creates an outline, and attaches it to this one.
   /// When the outline is selected, the supplied region is displayed.
   ///
-  /// Note: the coordiates are in User space. They are converted to User
+  /// Note: the coordinates are in User space. They are converted to User
   /// space.
   ///
   /// This allows you to have an outline for say a Chapter,
@@ -98,7 +98,7 @@ class PdfOutline extends PdfObject {
       params["/Parent"] = parent.ref();
       params["/Dest"] = PdfStream.array(dests);
 
-      // were a decendent, so by default we are closed. Find out how many
+      // were a descendent, so by default we are closed. Find out how many
       // entries are below us
       int c = descendants();
       if (c > 0) {

@@ -39,7 +39,7 @@ class PdfOutput {
 
   /// This method writes a [PdfObject] to the stream.
   ///
-  /// @param ob [PdfObject] Obeject to write
+  /// @param ob [PdfObject] Object to write
   void write(PdfObject ob) {
     // Check the object to see if it's one that is needed in the trailer
     // object
@@ -52,10 +52,6 @@ class PdfOutput {
 
   /// This closes the Stream, writing the xref table
   void close() {
-    // we use baos to speed things up a little.
-    // Also, offset is preserved, and marks the begining of this block.
-    // This is required by Pdf at the end of the Pdf file.
-
     int xref = os.offset;
 
     os.putString("xref\n");

@@ -26,7 +26,7 @@ class PdfXref {
   /// The generation of the object, usually 0
   int generation = 0;
 
-  /// Creates a crossreference for a Pdf Object
+  /// Creates a cross-reference for a Pdf Object
   /// @param id The object's ID
   /// @param offset The object's position in the file
   /// @param generation The object's generation, usually 0