Welcome to a nightmare. If you have Excel worksheets, it's not as bad as it could be (=pasted as low resolution bitmap images to a MS Word document that you should stylize for CMYK printing)
Placing the worksheet to InD brings the numerical data, but no graphs. Copying and pasting brings a low resolution bitmap RGB image of the graph with uneditable texts.
In many cases Excel graphs do not at all fit to the wanted style of the final product. The graph is full of decorative details and the final work needs something minimalist and easy to read.
If the original worksheet is available or extractable from a Word document (depends on how the graph has been imported to Word), you can often reproduce an acceptable graph in Illustrator or other software by starting from the worksheet numbers. As often a good way is to simply redraw it and use the original as a reference.
If you need a crisp vector version of the graph, it sometimes can be extracted from a PDF in Illustrator. Print the worksheet (no gridlines!) as PDF an open it in Illustrator for fixing. As well you can copy and paste the graph to Illustrator.
"Sometimes" = when the graph is flat. 3D-ish graphs are uneditable in Illustrator. An example:
This is actual real word example, only text are changed. The customer had made the 3D pie. The flat version is my copy. Its style is changed to flat.
Both graphs become visible when the page is printed as PDF and opened in Illustrator. To edit the graphs you must release and remove an incredible number of clipping masks. If you copy and paste a graph to Illustrator you in addition must ungroup the parts several times until all group levels are free. In both cases the texts are editable text objects altough divided - one text box is broken to several text objects. Retyping is often the easiest fix. It is best done in InD.
The 3D pie is in PDF very complex. It's made of small splinters. Some of them are in Illustrator marked as "non native graphics, uneditable". Copying and pasting to Illustrator makes the 3D pie a bitmap image. Texts stay as text, but splintered.
The flat pie from the PDF (after releasing and removing the numerous clipping paths) is editable. The white gaps are separate shapes which are easy to remove.
If you copy and paste the flat pie to Illustrator, it needs several ungroupings and clipping mask releasings & removals. In layers panel you see that every object is a group which contains some shape or text and a clipping mask:
After ungroupings and releasing the clipping masks something difficult to explain appears:
When looking the panels, the pie slices seem to be simple strokeless paths, but in the image they seem to have a thick white stroke. They are not groups nor compound paths. (NOTE: this can be avoided by making a PDF)
In this phase it's a good idea to delete all unnecessary empty rectangles (=previous text frames and released clipping masks). After it you can remove the white parts, if needed:
- secure the texts (=lock or move aside)
- select all pie parts
- goto Object > Expand > fills and strokes
- goto Object > Compound Path > Release
Now everything seems to be broken:
But there's only white shapes covering the actual pie; 2 white shapes per one slice. One is for making the white border and another is for making a hole to show the colored slice below. Ungroup all and delete the white shapes:
Now the flat pie is ready to get proper colors and texts. That can be done also in InD.
You can add the needed strokes to pie slices. Here a white stroke is selected. In the strokes panel the alignment setting = inside and corner joints = round.
You see that redrawing a simple graph or building it with the graph tool isn't more complex than fixing one imported from Excel.
One trick: Saving the worksheet as old style XLS file and opening it in old Excel (2003 or earlier) reduces the internal complexity of graphs. It really pays off to test it, if the graph has complex curves and you have old Excel somewhere.
ADD: Just in this case the 3D appearance was absolutely wanted. But It was easy to add a gradient filled foot and distort the pie to ellipse.
The added foot is shown separately. 3D effect Extrude & Bevel is another possiblity to create thickness.