I am converting PowerPoint to PDF for embedding in a learning management system for college students. I’m using an up-to-date PPT from Office 365 and an up-to-date Acrobat from an Adobe subscription. I’m using the Acrobat plug-in to PPT and the “Save as Adobe PDF” menu choice.
The images in the PPT files are all PNG images with the exception of a couple of animated GIFs, which work as expected. All images have alt-text. The file I’m currently working with has 36 images. The alt-text in 34 of them transfers to PDF as expected. Two, always the same two, transfer without alt-text. I’ve cut the alt-text from PPT, pasted it into TextPad, then pasted back to try to be sure there are no control characters in there.
Neither of the problem images is animated. One of the problem images was converted from a PPT table with “Save as picture,” but many other images made the same way worked fine. Recreating the image from scratch didn’t help. The first failure was a slide with two non-overlapping pictures. There are two nearly identical slides, one with a PNG image of a truth table and an animated GIF of an AND gate symbol. That works as expected; both images have alt-text. A slide with an image of a truth table generated the same way and an animated GIF of an XOR gate symbol fails. The XOR gate has alt-text in the PDF but the truth table does not. Both the one that works and the one that doesn’t are inside a content placeholder box. The selection pane for the failed slide shows no stray objects.
The other problem image was converted from Visio and overlayed on top of some PPT art. Removing the PPT art fixed that one, so I’m down to one. (Thanks, Dr. Pippik)
Using vanilla Microsoft “Save as” and selecting PDF does work, but I lose having the speaker notes that appear as a tool-tip on a speech bubble icon at the top left of each slide. The students need those notes more than they need the alt-text, but the alt-text is required for accessibility.
So, a double-barreled question: what causes this, or how can I debug the problem to find the cause?
