diff --git a/pdf/model/model.go b/pdf/model/model.go
index 051083ac..5f5f353d 100644
--- a/pdf/model/model.go
+++ b/pdf/model/model.go
@@ -9,23 +9,24 @@ import (
 	. "github.com/unidoc/unidoc/pdf/core"
 )
 
-// A PDFModel is a higher level PDF construct which can be collapsed into a PDF primitive.
-// Each PDFModel has an underlying Primitive and vice versa.
-// Copies can be made, but care must be taken to do it properly.
+// PdfModel represents a high level PDF type which can be collapsed into a PDF primitive (typically a dictionary
+// contained within an indirect object).
 type PdfModel interface {
 	ToPdfObject() PdfObject
 	GetContainingPdfObject() PdfObject
 }
 
-// The model manager is used to cache Primitive <-> Model mappings where needed.
-// In many cases only Model -> Primitive mapping is needed and only a reference to the Primitive
-// is stored in the Model.  In some cases, the Model needs to be found from the Primitive,
+// modelManager is used to cache PdfObject <-> Model mappings where needed.
+// In many cases only Model -> PdfObject mapping is needed and only a reference to the PdfObject
+// is stored in the Model.  In some cases, the Model needs to be found given the PdfObject,
 // and that is where the modelManager can be used (in both directions).
 //
 // Note that it is not always used, the Primitive <-> Model mapping needs to be registered
 // for each time it is used.  Thus, it is only used for special cases, commonly where the same
-// object is used by two higher level objects. (Example PDF Widgets owned by both Page Annotations,
-// and the interactive form - AcroForm).
+// object is used by two higher level objects.
+//
+// Example use case: PDF Annotation Widgets can be referenced by both Page Annotations, and the interactive
+// form - AcroForm. With the cache, can check if already loaded and get the underlying model without duplication.
 type modelManager struct {
 	primitiveCache map[PdfModel]PdfObject
 	modelCache     map[PdfObject]PdfModel