Sometimes clients ask us if we have any recommendations for the PDFs that they use to make flipbooks. While basically anything goes, there are a few things that could be useful for you to know if you design the PDF yourself, or want to pass some guidelines to the person who designs it for you.
Should I use a specific PDF format or version?
Almost all PDFs import perfectly fine, you don't have to use a specific format. The only exception is XFA. This format is used for PDFs that are enriched with forms that you can fill out. Adobe itself says that “In many ways, the XFA PDF file format is closer to an HTML file than it is to a traditional PDF file.“ If you have Adobe Acrobat Pro, then you can ‘distill’ the PDF to turn it back into an ordinary PDF, which you can import without any problem. You’ll lose the forms though.
When it comes to the PDF version (a.k.a. Acrobat compatibility level) we’d recommend avoiding PDF 1.3 (Acrobat 4.0). Overlapping images may get 'sliced up' in this PDF version. If you inspect the PDF very carefully, you will also notice tiny white lines.
During the conversion to a FlippingBook, the effect gets more pronounced. To correct this, try to generate the PDF again in the software where you designed it, and then export it in at least PDF 1.4 (Acrobat 5.0) format. Please note that just saving a 1.3 PDF in 1.4 format won't help - what is already broken won't get fixed this way.
What quality should I use for my images/how many DPI?
There is no need to use more than 150 DPI and anything over 225 DPI is basically wasted. FlippingBooks are intended for on-screen presentation, so we resize large images in such a way that they still look good, but are not so big that loading them slows down the user experience. In fact, if you use very detailed images (600 DPI or more) then the resizing may make them even look worse!
Any tips for text?
- When it comes to text, make sure that text in the PDF is real text (i.e. it has a font, color, and font size). Text that is part of an image is rendered very poorly. When you use real text, it will be converted to an SVG image. That means that is scales very well and looks crisp and clear at all zoom levels.
- Use a decent font size. With two pages visible at the same time in a browser, your pages often appear smaller on-screen than in hardcopy versions. Therefore, to keep text readable, make sure that you use a decent font size.
- Avoid 'hidden text'. It is much better to delete invisible text completely than to hide it behind other objects, put it in hidden layers, or making it the same color. Hidden text sometimes prevents us from generating the SVG image for the other text. While your normal text will still be visible, it may be a bit less crispy. You can check for hidden text in Acrobat Acrobat: Tools > Protection > Remove hidden information > Hidden text. Don't enable the other 'hidden information' options like 'Deleted or cropped content' and certainly not 'overlapping objects'.
- Don't use vertical text. If you really need to, then just use several elements of horizontal texts under each other.
Can I use different sized pages?
We don’t recommend different sized pages, even though it won’t cause any technical errors. One of the characteristics of our flipbooks is that all pages have the same size. So if you use different sizes, we will add extra white space around your pages to compensate. That looks a bit strange.
Finally, make sure your PDF doesn't have crop marks. Sometimes you can see small lines in the corners of your flipbook looking something like this:
These lines show where the paper should be cut after printing by professional printers. You can crop your PDF with Adobe Acrobat. You can also use free online tools like Sejda or PDF Resizer.