Hi,
unfourtunately it is not possible to open a file which is attached to an infopath form do some changes and save it back.
An idea would be to have a custom button on your form which allows you to browse your dircretory to select a file you want to attached.
Store the file path in a textbox control in you form, like this you can then use copy or move function in the next step.
Then you need a second button to submit your form and also automatically saves the file to a fix network folder or sharepoint library. Store this complete path also in a textbox and you it as a datasource for a Hyperlink control wihtin your document.
Like this the file is directly accessible via the hyperlilnk, can be changed, saveed and you are done.
Would this help ?
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