What file formats do you work with?
I work with most file formats commonly used in MS Office (e.g., Word, Excel, PowerPoint) and those supported by SDL Studio (among others it allows me to translate xml files).
If your document is in a specialized format, such as InDesign, it can often be saved in a compatible format for translation.
For PDF files, I cannot translate directly within the file. If proofreading is required, I use comments within the PDF. For translation, I use OCR software to convert the file into an editable format, but this additional step may involve an extra fee.