Lines around frames after export

[defaultyrj6dcmz20o7]

When i export my document to PDF, interactive or print, it shows thin black/grey lines around some of my images. It appears to be the end of the image within the frame, as it disappears when i shuffle these out. 

They don't print, and are not visible at all Zoom levels, but i want to add the doc up digitally so need them to be gone. 

Does anyone know how to fix this or what this is? 

[John Mensinger]

It looks like "stitching," and it's related to transparency flattening. This article call's them "white lines," but their percieved color can change depending on the colors behind them.

https://creativepro.com/when-you-see-thin-white-lines-in-your-pdf-files/

[BobLevine]

Interactive PDF does not flatten transparency but the graphics themselves may be flattened from their source. That screenshot the OP supplied is too small to tell.

[Luke Jennings3]

Do you have access to the original images? How are you saving them? I suggest saving them as vector (PDF), if possible, or include more white space around the image. If saving as an image from Illustrator, add a white box behind the chart to create a border or select the "use Artboard" option when saving.