There has been many Questions recently about drawing PDF&#39;s. 

Yes, you can render PDF&#39;s very easily with a `UIWebView` but this cant give the performance and functionality that you would expect from a good PDF viewer.



You can draw a PDF page &lt;a href=&quot;http://www.cocoabuilder.com/archive/cocoa/196313-display-pdf-in-calayer.html&quot;&gt;to a CALayer&lt;/a&gt; or &lt;a href=&quot;https://stackoverflow.com/questions/3831304/calayer-and-off-screen-rendering/3853778#3853778&quot;&gt; to a UIImage&lt;/a&gt;. Apple even have sample code to show how draw a large PDF &lt;a href=&quot;http://developer.apple.com/library/ios/#samplecode/ZoomingPDFViewer/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010281&quot;&gt;in a Zoomable UIScrollview&lt;/a&gt;


But the same issues keep cropping up.

**UIImage Method:**

 1. PDF&#39;s in a `UIImage` don&#39;t optically
    scale as well as a Layer approach.
 2. The CPU and memory hit on generating
    the `UIImages` from a `PDFcontext`
    limits/prevents using it to create a
    real-time render of new zoom-levels.


**CATiledLayer Method:**

 3. Theres a significant Overhead (time)
    drawing a full PDF page to a `CALayer`: individual tiles can be seen rendering (even with a tileSize tweak)
 4. `CALayers` cant be prepared ahead  of
        time (rendered off-screen).


Generally PDF viewers are pretty heavy on memory too. Even monitor the memory usage of apple&#39;s zoomable PDF example.


In my current project, I&#39;m developing a PDF viewer and am rendering a `UIImage` of a page in a separate thread (issues here too!) and presenting it while the scale is x1. `CATiledLayer` rendering kicks in once the scale is &gt;1.  iBooks takes a similar double take approach as if you scroll the pages you can see a lower res version of the page for just less than a second before a crisp version appears.

Im rendering 2 pages each side of the page in focus so that the PDF image is ready to mask the layer before it starts drawing.Pages are destroyed again when they are +2 pages away from the focused page.


**Does anyone have any insights, no matter how small or obvious to improve the performance/ memory handling of Drawing PDF&#39;s? or any other issues discussed here?**



***EDIT:*** Some Tips (Credit- Luke Mcneice,VdesmedT,Matt Gallagher,Johann):

- Save any media to disk when you can.

- Use larger tileSizes if rendering on TiledLayers

- init frequently used arrays with placeholder objects, alternitively another design approach is &lt;a href=&quot;http://cocoawithlove.com/2009/01/multiple-virtual-pages-in-uiscrollview.html&quot;&gt;this one&lt;/a&gt;

- Note that images will render faster than a `CGPDFPageRef`

- Use `NSOperations` or GCD &amp; &lt;a href=&quot;http://thirdcog.eu/pwcblocks/&quot;&gt;Blocks&lt;/a&gt; to prepare pages ahead
of time.

- call `CGContextSetInterpolationQuality(ctx, kCGInterpolationHigh); CGContextSetRenderingIntent(ctx, kCGRenderingIntentDefault);` before `CGContextDrawPDFPage` to reduce memory usage while drawing 

- init&#39;ing your `NSOperations` with a docRef is a bad idea (memory), wrap the docRef into a singleton.

- Cancel needless `NSOperations` When you can, especially if they will be using memory, beware of leaving contexts open though!

- Recycle page objects and destroy unused views

- Close any open Contexts as soon as you don&#39;t need them

- on receiving memory warnings release and reload the DocRef and any page Caches


**Other PDF Features:**


- &lt;a href=&quot;https://stackoverflow.com/questions/3257057/iphone-cgpdfdocument-pdf-links&quot;&gt;Getting Links inside a PDF&lt;/a&gt; (and &lt;a href=&quot;https://stackoverflow.com/questions/4080373/get-pdf-hyperlinks-on-ios-with-quartz&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;http://pastebin.com/69JW1Kkc&quot;&gt;here&lt;/a&gt;)

 - &lt;a href=&quot;https://stackoverflow.com/questions/4255298/how-does-an-annot-cgpdfdictionary-rect-translate-to-objective-c-points/4255586#4255586&quot;&gt;Understanding the PDF Rect for link positioning&lt;/a&gt;

 - &lt;a href=&quot;https://stackoverflow.com/questions/4303394/converting-adobe-pdf-date-string-to-nsdate&quot;&gt;Converting PDF annot datestrings&lt;/a&gt;

 - [Getting the target of the link](https://stackoverflow.com/questions/4643489/how-do-i-retrieve-a-page-number-or-page-reference-for-an-outline-destination-in-a/4683905#4683905) (Getting the page number from the `/Dest` array)

- &lt;a href=&quot;https://stackoverflow.com/questions/2556344/create-a-table-of-contents-from-a-pdf-file&quot;&gt;Getting a table of contents&lt;/a&gt;

- [Document title](https://stackoverflow.com/questions/5881921/get-cgpdfdocumentref-name-of-document/5912618#5912618) and &lt;a href=&quot;http://www.iphonedevsdk.com/forum/iphone-sdk-development/29770-pdf-title-keywords-label.html&quot;&gt;Keywords&lt;/a&gt;

- &lt;a href=&quot;https://stackoverflow.com/questions/2556344/create-a-table-of-contents-from-a-pdf-file/3427596#3427596&quot;&gt;Getting Raw Text&lt;/a&gt; (and &lt;a href=&quot;https://stackoverflow.com/questions/2960195/extracting-pdf-text-in-objective-c&quot;&gt;here&lt;/a&gt; and &lt;a href=&quot;https://stackoverflow.com/questions/3627745&quot;&gt;Here&lt;/a&gt; and &lt;a href=&quot;https://stackoverflow.com/questions/3627745/getting-text-position-while-parsing-pdf-with-quartz-2d&quot;&gt;here&lt;/a&gt; (positioning focused))

- &lt;a href=&quot;http://blog.random-ideas.net/?p=184&quot;&gt;Searching&lt;/a&gt;(and &lt;a href=&quot;https://stackoverflow.com/questions/4097044/pdf-search-on-the-iphone&quot;&gt;here&lt;/a&gt;) (doesn&#39;t work with all PDFs (some just show weird characters, I guess it&#39;s an encoding issue but I&#39;m not sure) -Credit BrainFeeder)

- &lt;a href=&quot;https://stackoverflow.com/questions/3831304/calayer-and-off-screen-rendering&quot;&gt;CALayer and Off-Screen Rendering&lt;/a&gt; - render the next page for fast/smooth display

**Documentation**

 - &lt;a href=&quot;http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CGPDFObject/Reference/reference.html&quot;&gt;Quartz PDFObjects&lt;/a&gt; (Used for meta info, annotations, thumbs) 
 - &lt;a href=&quot;http://www.adobe.com/devnet/pdf/pdf_reference.html&quot;&gt;Abobe PDF Spec&lt;/a&gt; 


**Example projects**

 - [Apple/ ZoomingPDF](http://developer.apple.com/library/ios/#samplecode/ZoomingPDFViewer/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010281) - zooming, `UIScrollView`, `CATiledLayer`
 - [vfr/ reader](https://github.com/vfr/Reader) - zooming, paging, `UIScrollView`, `CATiledView`
 - [brow/ leaves](https://github.com/brow/leaves) - paging with nice transitions 
 - [/ skim](http://skim-app.sourceforge.net/developers.html) - everything it seems (PDF reader/editor for OSX)


All Apple Pdfkit Solutions on Gang of Coders

Total of 1 Apple Pdfkit Solutions

Fast and Lean PDF Viewer for iPhone / iPad / iOS - tips and hints?