In order to get the best results when merging images into a document, it's important to properly set up the placeholder image. This applies whether you're using Picture Content Controls or Bookmarks to merge your content.
There are two separate issues to consider here, the size and position of the image. Before we get started, here's a quick explanation of how to access the relevant tools you'll need to complete the actions in this article.
Right-clicking on an image will reveal the Picture Format menu. Selecting 'Size and Position' (near the bottom of the menu) opens the 'Layout' dialogue. The tabs within the Layout dialogue include Position, Text Wrapping and Size. We'll deal with all of those.
When images uploaded into the form are merged into the generated document, they are shrunk (or expanded) to match the dimensions of the placeholder image whilst keeping their aspect ratio constant. For example, if you merge an image that was 800*600 pixels when uploaded into a placeholder image that is 200*200 pixels, the resulting image in the document will be 200*150 pixels. In more technical terms, the largest dimension of the original image will be shrunk to fit the placeholder image and the ratio of dimensions in the original image will be applied to the resulting image.
This means that you need to keep the size and shape of the uploaded images in mind when sizing your placeholder image. Merging an image that is tall and narrow into a short and wide placeholder will have poor results.
Text Wrapping and Image Position
Getting the position of an image right is absolutely crucial, particularly when it's part of other conditional content. The first thing to decide when placing an image is whether you want it to sit in a 'fixed' position on the page or be part of another content block. This is what's known as 'Text Wrapping'.
As you can see from Word's Layout dialogue, there are lots of different ways to have the picture sit in or around your text. This is mostly a stylistic decision but it's also important in the context of making sure it sits properly inside other or around conditional content. The top row of Wrapping styles in the dialogue below will all have the image sitting within another text block which is the most likely choice if you have a small image that illustrates a particular point within that text block. This is the easiest choice and once you've inserted the image (either with a picture content control or with a bookmark) you more-or-less know what it will look like in the output document. The only thing left to decide is how tightly you'd like the text to wrap around the image. (Note that the bottom half of the dialogue becomes available and relevant only if you choose the 'Square, Tight or Through' styles).
If, on the other hand, you don't want your image to be part of other content, the process of placement becomes a bit more involved. You'll need to select either the 'Behind text' or 'In front of text' style and then move onto the Position tab which you can see below.
Understanding all the choices in this dialogue goes beyond the context of this article, but we'll give you a few pointers to get the best result. If you want your image to sit at a fixed position on the page regardless of what else appears in the document, you should select 'Absolute position' for both Horizontal and Vertical position. You then need to 'anchor' your image to a point on the page which will be both 'visible' and static in your output document. This ensures that the image won't accidentally be left out or migrate to a different page if the preceding or following content changes. Once you've found that point, you can 'lock' the image's anchor in the Layout dialogue which will change the icon from blue to black with a padlock.
The final step is to simply place the image itself in the right location on the page which can be done by dragging with the mouse or manually using the coordinates in the dialogue.