![]() #ANNOTATE ON PDF PDF#This makes it easy for our customers to work with annotations without any prior knowledge of the PDF file format.Annotation is the process of adding extra pieces of information to a document. It hides implementation details and complex interactions between various annotation properties. The PSPDFKit SDK provides a facade that exposes annotation dictionaries as regular objects of your programming language of choice. The PDF annotation model is quite complex. The PSPDFKit SDK allows you to parse and create appearance streams. #ANNOTATE ON PDF HOW TO#An appearance stream is a set of drawing commands that tells a PDF viewer precisely how to render an annotation (independent of the visual properties defined in the annotation’s dictionary). To solve this problem, each annotation can define an appearance stream that should be used for rendering the annotation. However, these don’t guarantee that the annotation will be displayed the same in different PDF viewers. Appearance StreamsĪnnotations may contain properties that describe their appearance - such as annotation color or shape. You can find all the details about how annotations are stored inside PDF documents in section 8.4 of Adobe’s PDF specification. The annotation type specifies which additional keys can be present in the annotation dictionary and which keys are required.īelow is an example of a page dictionary: Subtype specifies one of the supported annotation types. Rect specifies the rectangle (in page coordinates) where the annotation is going to be positioned on the page. Each annotation dictionary contains at least two keys: Similarly, annotations are also represented by their own dictionaries. Each page is represented by its own dictionary that contains separate entries for page content and for annotations associated with the page. The top-level dictionary in a PDF document contains a list of pages in the document. ![]() An example of another PDF object is a content stream that contains lists of drawing operations or binary image data. The document tree is formed from dictionaries of key-value pairs that can contain other dictionaries as values. The PDF Annotation ModelĪ PDF document is a collection of data objects organized into a tree structure. These include buttons, checkboxes, combo boxes, and more. Widget annotations are used to implement interactive forms. #ANNOTATE ON PDF MOVIE#This includes sound annotations, movie annotations, and even 3D content. Two annotation types can be used to add notes to the page:įree-text annotations for adding a floating text boxĪnnotations can also be used to add multimedia content to the page. Stamp annotations can be used when simple shapes drawn with drawing annotations aren’t sufficient - for example, when you want to draw a complex raster or vector image. Ink annotations for completely freeform drawing connecting a list of points into Bézier curvesĪll of these support the usual drawing properties such as color, line thickness, fill color (for filled shapes), or line styles (e.g. Polygon and polyline annotations for drawing polygonal lines Square and circle annotations for drawing squares/rectangles and circles/ellipses These include text highlight, underline, or strikeout annotations.ĭifferent annotations can be used for drawing on top of a PDF page. ![]() The simplest types of markup annotations are text markup annotations for marking up page text. ![]() Non-markup annotations that are used for other purposes - these include interactive forms and multimedia Markup annotations that are primarily used to mark up the content of a PDF document The PDF specification defines two categories for annotations: Regardless of the annotation types that can be created, PDF viewers conforming to the PDF specification should also support rendering for all annotation types. text highlights, notes, lines, or shapes. ![]() PDF viewers usually allow the creation and editing of various annotation types, e.g. These objects are called annotations, and their purpose ranges from marking up page content to implementing interactive features such as forms. Finally, it will outline how PSPDFKit maps this representation to an easy-to-use annotation model.Ĭontent displayed as a PDF page isn’t suitable for easy editing, but the PDF specification defines a comprehensive set of objects that can be added to PDF pages without changing the page content. It will also look into how annotations are represented inside a PDF document. This post will discuss what PDF annotations are, exploring which types of annotations are defined by the PDF specification. ![]()
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