diff --git a/CHANGES.md b/CHANGES.md
index 98b42d1..6399488 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,7 @@ v1.1.0 (Month DD, YYYY)
 -----------------------
 
 - Added `pdfioFileCreateTemporary` function (Issue #29)
+- Added `pdfioDictIterateKeys` function (Issue #31)
 
 
 v1.0.1 (March 2, 2022)
diff --git a/doc/pdfio.3 b/doc/pdfio.3
index 87e25e7..ad9a061 100644
--- a/doc/pdfio.3
+++ b/doc/pdfio.3
@@ -1,4 +1,4 @@
-.TH pdfio 3 "pdf read/write library" "2022-05-15" "pdf read/write library"
+.TH pdfio 3 "pdf read/write library" "2022-06-27" "pdf read/write library"
 .SH NAME
 pdfio \- pdf read/write library
 .SH Introduction
@@ -1950,6 +1950,31 @@ pdfio_valtype_t  pdfioDictGetType (
     const char *key
 );
 .fi
+.SS pdfioDictIterateKeys
+Iterate the keys in a dictionary.
+.PP
+.nf
+void pdfioDictIterateKeys (
+    pdfio_dict_t *dict,
+    pdfio_dict_cb_t cb,
+    void *cb_data
+);
+.fi
+.PP
+This function iterates the keys in a dictionary, calling the supplied
+function "cb":
+.PP
+.nf
+    bool
+    my_dict_cb(pdfio_dict_t *dict, const char *key, void *cb_data)
+    {
+    ... "key" contains the dictionary key ...
+    ... return true to continue or false to stop ...
+    }
+
+.fi
+The iteration continues as long as the callback returns \fBtrue\fR or all keys
+have been iterated.
 .SS pdfioDictSetArray
 Set a key array in a dictionary.
 .PP
@@ -2889,6 +2914,12 @@ Standard color spaces
 .nf
 typedef enum pdfio_cs_e pdfio_cs_t;
 .fi
+.SS pdfio_dict_cb_t
+Dictionary iterator callback
+.PP
+.nf
+typedef bool(*)(pdfio_dict_t *dict, const char *key, void *cb_data) pdfio_dict_cb_t;
+.fi
 .SS pdfio_dict_t
 Key/value dictionary
 .PP
diff --git a/doc/pdfio.html b/doc/pdfio.html
index db000b9..c134456 100644
--- a/doc/pdfio.html
+++ b/doc/pdfio.html
@@ -360,6 +360,7 @@ span.string {
 <li><a href="#pdfioDictGetRect">pdfioDictGetRect</a></li>
 <li><a href="#pdfioDictGetString">pdfioDictGetString</a></li>
 <li><a href="#pdfioDictGetType">pdfioDictGetType</a></li>
+<li><a href="#pdfioDictIterateKeys">pdfioDictIterateKeys</a></li>
 <li><a href="#pdfioDictSetArray">pdfioDictSetArray</a></li>
 <li><a href="#pdfioDictSetBinary">pdfioDictSetBinary</a></li>
 <li><a href="#pdfioDictSetBoolean">pdfioDictSetBoolean</a></li>
@@ -443,6 +444,7 @@ span.string {
 <li><a href="#TYPES">Data Types</a><ul class="subcontents">
 <li><a href="#pdfio_array_t">pdfio_array_t</a></li>
 <li><a href="#pdfio_cs_t">pdfio_cs_t</a></li>
+<li><a href="#pdfio_dict_cb_t">pdfio_dict_cb_t</a></li>
 <li><a href="#pdfio_dict_t">pdfio_dict_t</a></li>
 <li><a href="#pdfio_encryption_t">pdfio_encryption_t</a></li>
 <li><a href="#pdfio_error_cb_t">pdfio_error_cb_t</a></li>
@@ -2262,6 +2264,33 @@ const char *pdfioDictGetString(<a href="#pdfio_dict_t">pdfio_dict_t</a> *dict, c
 </tbody></table>
 <h4 class="returnvalue">Return Value</h4>
 <p class="description">Value type</p>
+<h3 class="function"><a id="pdfioDictIterateKeys">pdfioDictIterateKeys</a></h3>
+<p class="description">Iterate the keys in a dictionary.</p>
+<p class="code">
+void pdfioDictIterateKeys(<a href="#pdfio_dict_t">pdfio_dict_t</a> *dict, <a href="#pdfio_dict_cb_t">pdfio_dict_cb_t</a> cb, void *cb_data);</p>
+<h4 class="parameters">Parameters</h4>
+<table class="list"><tbody>
+<tr><th>dict</th>
+<td class="description">Dictionary</td></tr>
+<tr><th>cb</th>
+<td class="description">Callback function</td></tr>
+<tr><th>cb_data</th>
+<td class="description">Callback data</td></tr>
+</tbody></table>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">This function iterates the keys in a dictionary, calling the supplied
+function &quot;cb&quot;:
+
+<pre>
+bool
+my_dict_cb(pdfio_dict_t *dict, const char *key, void *cb_data)
+{
+... &quot;key&quot; contains the dictionary key ...
+... return true to continue or false to stop ...
+}
+</pre>
+The iteration continues as long as the callback returns <code>true</code> or all keys
+have been iterated.</p>
 <h3 class="function"><a id="pdfioDictSetArray">pdfioDictSetArray</a></h3>
 <p class="description">Set a key array in a dictionary.</p>
 <p class="code">
@@ -3514,6 +3543,11 @@ typedef struct _pdfio_array_s pdfio_array_t;
 <p class="code">
 typedef enum <a href="#pdfio_cs_e">pdfio_cs_e</a> pdfio_cs_t;
 </p>
+<h3 class="typedef"><a id="pdfio_dict_cb_t">pdfio_dict_cb_t</a></h3>
+<p class="description">Dictionary iterator callback</p>
+<p class="code">
+typedef bool (*pdfio_dict_cb_t)(<a href="#pdfio_dict_t">pdfio_dict_t</a> *dict, const char *key, void *cb_data);
+</p>
 <h3 class="typedef"><a id="pdfio_dict_t">pdfio_dict_t</a></h3>
 <p class="description">Key/value dictionary</p>
 <p class="code">
diff --git a/pdfio-dict.c b/pdfio-dict.c
index a5ae739..e15aebd 100644
--- a/pdfio-dict.c
+++ b/pdfio-dict.c
@@ -464,6 +464,47 @@ _pdfioDictGetValue(pdfio_dict_t *dict,	// I - Dictionary
 }
 
 
+//
+// 'pdfioDictIterateKeys()' - Iterate the keys in a dictionary.
+//
+// This function iterates the keys in a dictionary, calling the supplied
+// function "cb":
+//
+// ```
+// bool
+// my_dict_cb(pdfio_dict_t *dict, const char *key, void *cb_data)
+// {
+// ... "key" contains the dictionary key ...
+// ... return true to continue or false to stop ...
+// }
+// ```
+//
+// The iteration continues as long as the callback returns `true` or all keys
+// have been iterated.
+//
+
+void
+pdfioDictIterateKeys(
+    pdfio_dict_t    *dict,		// I - Dictionary
+    pdfio_dict_cb_t cb,			// I - Callback function
+    void            *cb_data)		// I - Callback data
+{
+  size_t	i;			// Looping var
+  _pdfio_pair_t	*pair;			// Current pair
+
+
+  // Range check input...
+  if (!dict || !cb)
+    return;
+
+  for (i = dict->num_pairs, pair = dict->pairs; i > 0; i --, pair ++)
+  {
+    if (!(cb)(dict, pair->key, cb_data))
+      break;
+  }
+}
+
+
 //
 // '_pdfioDictRead()' - Read a dictionary from a PDF file.
 //
diff --git a/pdfio.h b/pdfio.h
index 6b88c9a..9ba328b 100644
--- a/pdfio.h
+++ b/pdfio.h
@@ -55,6 +55,8 @@ typedef struct _pdfio_array_s pdfio_array_t;
 					// Array of PDF values
 typedef struct _pdfio_dict_s pdfio_dict_t;
 					// Key/value dictionary
+typedef bool (*pdfio_dict_cb_t)(pdfio_dict_t *dict, const char *key, void *cb_data);
+					// Dictionary iterator callback
 typedef struct _pdfio_file_s pdfio_file_t;
 					// PDF file
 typedef bool (*pdfio_error_cb_t)(pdfio_file_t *pdf, const char *message, void *data);
@@ -165,6 +167,7 @@ extern pdfio_obj_t	*pdfioDictGetObj(pdfio_dict_t *dict, const char *key) _PDFIO_
 extern pdfio_rect_t	*pdfioDictGetRect(pdfio_dict_t *dict, const char *key, pdfio_rect_t *rect) _PDFIO_PUBLIC;
 extern const char	*pdfioDictGetString(pdfio_dict_t *dict, const char *key) _PDFIO_PUBLIC;
 extern pdfio_valtype_t	pdfioDictGetType(pdfio_dict_t *dict, const char *key) _PDFIO_PUBLIC;
+extern void		pdfioDictIterateKeys(pdfio_dict_t *dict, pdfio_dict_cb_t cb, void *cb_data) _PDFIO_PUBLIC;
 extern bool		pdfioDictSetArray(pdfio_dict_t *dict, const char *key, pdfio_array_t *value) _PDFIO_PUBLIC;
 extern bool		pdfioDictSetBinary(pdfio_dict_t *dict, const char *key, const unsigned char *value, size_t valuelen) _PDFIO_PUBLIC;
 extern bool		pdfioDictSetBoolean(pdfio_dict_t *dict, const char *key, bool value) _PDFIO_PUBLIC;
diff --git a/testpdfio.c b/testpdfio.c
index dccc451..d17c803 100644
--- a/testpdfio.c
+++ b/testpdfio.c
@@ -34,6 +34,7 @@ static int	do_test_file(const char *filename, int objnum, bool verbose);
 static int	do_unit_tests(void);
 static int	draw_image(pdfio_stream_t *st, const char *name, double x, double y, double w, double h, const char *label);
 static bool	error_cb(pdfio_file_t *pdf, const char *message, bool *error);
+static bool	iterate_cb(pdfio_dict_t *dict, const char *key, void *cb_data);
 static ssize_t	output_cb(int *fd, const void *buffer, size_t bytes);
 static const char *password_cb(void *data, const char *filename);
 static int	read_unit_file(const char *filename, size_t num_pages, size_t first_image, bool is_output);
@@ -507,6 +508,8 @@ do_unit_tests(void)
   size_t		first_image,	// First image object
 			num_pages;	// Number of pages written
   char			temppdf[1024];	// Temporary PDF file
+  pdfio_dict_t		*dict;		// Test dictionary
+  int			count = 0;	// Number of key/value pairs
   static const char	*complex_dict =	// Complex dictionary value
     "<</Annots 5457 0 R/Contents 5469 0 R/CropBox[0 0 595.4 842]/Group 725 0 R"
     "/MediaBox[0 0 595.4 842]/Parent 23513 0 R/Resources<</ColorSpace<<"
@@ -968,6 +971,41 @@ do_unit_tests(void)
 
   // TODO: Test for known values in this test file.
 
+  // Test dictionary APIs
+  fputs("pdfioDictCreate: ", stdout);
+  if ((dict = pdfioDictCreate(inpdf)) != NULL)
+  {
+    puts("PASS");
+
+    fputs("pdfioDictSet*: ", stdout);
+    if (pdfioDictSetBoolean(dict, "Boolean", true) && pdfioDictSetName(dict, "Name", "Name") && pdfioDictSetNumber(dict, "Number", 42.0) && pdfioDictSetString(dict, "String", "String"))
+    {
+      puts("PASS");
+    }
+    else
+    {
+      puts("FAIL");
+      return (1);
+    }
+
+    fputs("pdfioDictIterateKeys: ", stdout);
+    pdfioDictIterateKeys(dict, iterate_cb, &count);
+    if (count == 4)
+    {
+      puts("PASS");
+    }
+    else
+    {
+      printf("FAIL (got %d, expected 4)\n", count);
+      return (1);
+    }
+  }
+  else
+  {
+    puts("FAIL");
+    return (1);
+  }
+
   // Test the value parsers for edge cases...
   fputs("_pdfioValueRead(complex_dict): ", stdout);
   s = complex_dict;
@@ -1212,6 +1250,27 @@ error_cb(pdfio_file_t *pdf,		// I  - PDF file
 }
 
 
+//
+// 'iterate_cb()' - Test pdfioDictIterateKeys function.
+//
+
+static bool				// O - `true` to continue, `false` to stop
+iterate_cb(pdfio_dict_t *dict,		// I - Dictionary
+           const char   *key,		// I - Key
+           void         *cb_data)	// I - Callback data
+{
+  int	*count = (int *)cb_data;	// Pointer to counter
+
+
+  if (!dict || !key || !cb_data)
+    return (false);
+
+  (*count)++;
+
+  return (true);
+}
+
+
 //
 // 'output_cb()' - Write output to a file.
 //