When viewing some PDFs within the app, you might occasionally notice a lag when scrolling through your PDF content. For some other PDFs, some or all images in them might not be shown at all.
This can be down to multiple factors and usually involves the file size and/or the original PDF encoder of the PDF. If you notice the same issue in the Files app or macOS Preview, this is unfortunately not in our control because the app uses Apple's PDF rendering engine.
Possible Side Effects
The slowly or badly rendered PDF might cause other issues as well. For example:
- Scrolling through its pages might crash the app (due to the computing required to render those pages).
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Exporting it to a PDF produces one with duplicate page backgrounds (presumably because of the delayed rendering, or the special way the original PDF was created).
- Some original PDFs, like those from NCERT, have copyright watermarks on all the pages. If you import such a PDF, then export it from the app, the exported PDF might also include an unintended black box on the page.
- Some PDF elements, like images, are rendered incorrectly, if at all.
Workarounds
Compress the PDF (recommended for most PDFs)
If you don't have a Mac, compress the PDF with a non-Adobe online tool, thereby changing the encoding method for the PDF, and try importing the result PDF. This is especially useful if you're experiencing effects #2 and #3 above.
Convert the PDF to an image-based one
The second best solution is to flatten the original PDF to remove all rendering issues.
Importing the new PDF to Goodnotes will resolve this issue, though you'll lose the ability to select or search for its text.
Reduce the PDF file size (macOS only)
Try opening the PDF in macOS Preview and clicking File > Export..., selecting "Reduce File Size" under "Quartz Filter" and importing the result PDF to see if the slow rendering improves.
Resize the source document
Better yet, if you have access to the source Keynote file, try the following:
- Open the file in Keynote and click the File menu > Reduce File Size... > Reduce a Copy.
- Open the reduced Keynote file, click Document in the right sidebar and resize the page size to Letter or smaller:
- Click File > Export To > PDF... > Next... > Export.
- Import the result PDF to see if the rendering improves.